Well, I think part of the reason is the target audiences.

In movies, they shoot for general audiences as horror usually, which means you just want big and scary, so the gender of the werewolf doesn't matter. They'll just be big and scary with little character development anyway, so the male dominated industry just sticks with the default.

In books, however, the target audience now is the paranormal romance audience, which skews heavily female. You'd think this would result in more werewolf women being the main character, but it's the opposite. The readers don't want to be werewolves, they want the fantasy of fucking them and taming the bad boy (the genre is very much a hetero dominated one). So the viewpoint character is most often going to be just some woman drawn into whatever the situation is.

Mind you, we're talking traditionally published here, there's plenty of casual writers putting stories out on an archive of our own.

However, the field is not empty! Forgive the source, butGoodreads is still good about being able to find things by topic

The third one on that list, Bitten, is part of a fairly decent series that isn't just soft core erotica or pure romance. Leans little heavy into the whole "alpha" bullshit with the werewolves, but that's a matter of taste.

Some of those are even more standard urban fantasy rather than paranormal romance, though I've found that any urban fantasy with a female protagonist is usually going to include romance at some point.

Anyway, I still think it comes down to writers/producers having a target audience, and putting out what they think will profit rather than primarily trying to explore a concept in depth. You really don't see much of that in any genre tbh, what with so many production companies and publishers wanting only to invest in something that sells, and having a narrow view of what that is.