Have you ever actually looked into people who do that? They put in a lot of effort into understanding the original creator, their intent, process, materials etc. The copies are still very much art as they are expressions of the imitator's feelings towards the work. Performing studies of popular art by trying to replicate it is a powerful tool for learning precisely because it allows you, as an artist, to understand how the original artist thought, helping you learn to think like an artist and leading you to develop your own ideas and means of expression.

AI is none of that.

>Would you object to somebody looking at your images and imitating the style?

Yes. It's quite difficult to do so, however. The people capable usually have better things to do with their skills.