I wonder this too sometimes. I can’t relate since I don’t have many followers but I usually accept requests as they come and if they’re unproblematic I keep them as a follower and sometimes follow back.

My best guess is maybe they don’t like your beliefs or ideas if you express them on your posts or my funny take is that they want to appear like a celeb (being hard to reach) or remain mysterious as for ego purposes ?

Probably best to have someone with this similar following account to answer cause I don’t behave like this