There are lots of galactic empires in science fiction. Lots and lots. Star Wars, many David Weber books, the Skolian books by Catherina Asaro and the Vorkosigan books by Lois Bujold. I am sure there many, many more that I am forgetting right now.
Today we live in a world where there aren’t that many ruling queens, kings and princes. Even where royal families still exist, the monarchs are usually figure heads.
That is why it is puzzling to me that so much space opera have kings, queens and royals with real power. I mean, we go a hundreds of years in the future and we revert to monarchies?
It just strikes me as a little strange. (But fun!)