I've had people comment on this before. There are several reasons I tend to write about empires and kingdoms, but please note that even most of the monarchies I write about (at least approvingly) have both input from those governed (which may or may not be called a parliament) and a means whereby an incompetent/corrupt monarch may be removed. I also write about monarchies/empires in transition towards other forms of government quite a lot, as well.
Historically, monarchy has a much longer track record than democracy, and outside a high-bandwidth society, real participatory government on a nationstate level is pretty thoroughly impractical. Note that in this case I'm using "bandwidth" in a rather sweeping sense which doesn't necessarily have anything to do with electronics. Electronic communication interfaces are good, but what I'm really speaking of here is a broad-based educational system and widespread news availability. Obviously it's possible for people to vote without possessing --- or availing themselves of --- either of the above (as some recent US elections demonstrate, whichever side of the political aisle one might be on), but the intelligent, effective use of the franchise means that the voters have to be at least reasonably well-informed upon the issues facing them (in a direct democracy) or their elected representatives (in a representative democracy). You don't get that sort of voters if the information they need isn't available to them, and that requires both sufficient education to access information and set it in a coherent context and avenues by which that information can reach them in the first place. While I can get seriously pissed off with the gentleman (and gentlewomen) of the Fourth Estate, widespread, open, and at least reasonably honest news reportage is essential to a functioning elective form of government.
Direct democracy begins to break down very rapidly once one gets beyond purely local government. Athens, so frequently referred to as the mother of democracy, had a very limited franchise and was not a very large social entity, whether in terms of population or geographic extent, compared to the vast majority of modern nationstates. In addition, whatever their other advantages (and I grant that the advantages are legion), elective forms of government tend to be less efficient in the face of an emergency than monarchial ones. Mind you, there's something to be said for governmental inefficiency under normal circumstances, given that government inevitably accrues all of the power it can. This isn't necessarily because the government in question is inherently evil, either. A government's job — its entire reason for being — is to govern, and it seeks the tools and authority it needs in order to accomplish that task. (The fact that governments tend to be made up of fallible, corruptible, and often corrupted human beings who seek power for reasons of ego, personal wealth, or any number of other regrettable motivations only makes a potentially bad situation worse in that respect.) However that may be, in times of great emergency, successful democratic/representative governments tend to adopt rules and procedures which vest enormous power in the state's executive with the understanding (or at least the hope) that the power in question will be returned to the electorate and/or its representatives once the emergency passes. And the reason they do that is because there isn't time for reasoned debate and to seek parliament/congress' approval of every decision or action.
One-person rule is more efficient (note that I did not say it was necessarily better) than a representative democracy, and a representative democracy is more efficient than a pure democracy. I think it should be evident that the empires and monarchies of which I write approvingly are generally constitutional monarchies with a powerful representative element. It should also be noted that I also write rather approvingly of representative democracy in general. The restored Peoples' Republic of Haven in the Honorverse is one example of that, I would say. So are quite a lot of the system and planetary governments in the Honorverse. Both the Protectorate of Grayson and the Star Kingdom of Manticore became monarchies for quite different reasons, but the trend even in both of those star nations is towards increasing representation. The Solarian League, on the other hand, is an example of one type of façade democracy, while several of the pre-annexation governments in the Talbott Cluster were examples of other sorts of façade democracy is.
From a literary perspective, there are some significant advantages in writing about monarchial governments, of course. It allows the writer to focus more directly on individual strong characters whose decisions have immediate impact and who become personally responsible for the outcomes of those decisions. It's clearly not impossible to come up with characters and situations where both that focus and that responsibility can also be achieved in non-monarchial systems, and I've done that, too. For example, Eloise Pritchart in the Republic of Haven has to work within the constraints of a representative democracy. It's easier and "cleaner" (at least in my opinion and experience) to work with someone who is expected by both his/her fellow citizens and by the reader to be able to make, implement, and "own" critical decisions of state quickly and on his/her own recognizance, however.
In a more general sense, I tend to believe that the jury is still out on the longevity, effectiveness, and universality of representative/democratic government. I happen to think that that type of government offers the greatest opportunities politically, economically, and in terms of "quality of life" to its citizens, but monarchies and empires of one sort or another have been around far longer and one need not look far to find autocracies masquerading as democracies all over the world today. I'm inclined to think that if/when we finally do get to the stars, effectively monarchial governments are likely to reemerge, although in the Honorverse I've tried to present specific reasons for their reemergence. In the case of Manticore, as a deliberate move by the original colonists to conserve their political power in a star nation which of necessity was about to absorb a huge influx of newcomers. In the case of Grayson, as a response to the critical survival imperatives of a rather intensely hostile environment. There could be any number of other "legitimate" reasons for that sort of transformation, and there could also be an even greater number of "illegitimate" reasons, including an unscrupulous political leader who seizes absolute power and makes it stand up. Four or five generations later, the descendents of even the most unscrupulous political leader imaginable may actually have become enlightened rulers with the best interests of their subjects in mind, whereas after the same time period, the descendents of even the most enlightened ruler can have become despots concerned only with their own self-interest and the preservation of their own power. Which way it goes in a specific literary universe depends on the story the writer wants to tell. In real life, the reasons and the consequences can be far messier and more painful.
I expect that most people have a tendency to subconsciously assume that the form of government under which they were born and raised is the inevitable, default form of government. We assume the permanence of what are actually transitory, perpetually evolving forms of government. Someone living in the United States of 1800 would be shocked by the power of the central government in the United States of 2000. For that matter, the changes in power structures, centers of authority, and routine government interference (for good or ill) in the personal lives of US citizens between 1950 and 2000 are enormous. They've happened so gradually, however, that the majority of American citizens take them for granted without ever really thinking about how transformative they've actually been. I try in my writing to show that evolutionary process in progress, and the truth is that most of the forms of government — and most of the specific governments — I write about are constantly in the process of becoming something else.
