Ask Lemmygrad

I wouldn't read so much intent into it, it's simply that monarchy and nobility have been at the core of the creation of cultural texts until very recently and the tropes are a comfortable common ground for media.

Most "classics" or famous books used as inspiration from before the 20th century are either about nobility or have them in the context in some way.

There's also a lot of "decadent king" or (specifically in Japanese anime) "Christianity bad" tropes, so I wouldn't say it's all glorification.

Though don't get me started on the whole "rightful ruler good king" plot beat that happens in so many otherwise good stories, like Fire Emblem.