To be fair, the novels targetted at straight women do this too with handsome men. Though, I prefer the protagonist to be on the cover.
The worst is when I see a title and it says something like queen of darkness, but the protagonist is a male. Come on!
A protagonist not being on the cover is a red flag to me. It lets me know that the story will have a generic/boring MC.
What do you mean I have to read until chapter 100+ before the girl in the cover appear in the story???