Werewolf movies used to be more popular than they are now, but werewolf books (or any kind of shapeshifter, but especially wolves) are hugely more popular than they were before, crossing the genres of SFF, horror, and romance.
Why might that be? Why are books full of werewolves and movies and TV are not? Maybe because zombie and vampire movies can be made on a small budget, but werewolves take a certain amount of special effects. Not a lot of special effects, but you need some, and vampires and zombies just need costumes.
Folklorically (is that a word—if not, it is now, I just invented it) speaking there were lots of ways to become a werewolf: bite or scratch of course. Spell (voluntary), or curse (involuntary). Die with some great sin like fratricide unredeemed. Or not even explained. Sometimes the werewolves in folklore or old literary tales just are, a mystery to the other characters in the story. From those stories, perhaps comes the idea of lycanthropy being hereditary. If no one knows how they became werewolves maybe they were born that way, and the author speculates from there.
Plus current fantasy readers like their supernaturals in groups. In the old days, vampires were solitary, but now they get put into covens like witches. Werewolves used to come in groups if they were witches or sorcerers using black magic spells, but such stories were rare. Most of the time werewolves were solitary, but now increasingly we see stories where they appear in packs. I think as someone said up above its the group dynamics that appeal to so many readers. Sure, a few people wrote popular books about hereditary werewolves living in packs, and other writers copied them because they were inspired by them or because they wanted to get on the bandwagon, but there was something there that readers really liked about the pack idea or those earlier books would not have been so popular and the books that followed after them would not have attracted readers and there wouldn't have been a bandwagon.
So what is the appeal of the pack that strikes such a chord now, and what was it about the lone supernatural that struck a similar chord before? Could it have something to do with how society is changing? Or is it simply writers sticking with what they know works (and when I say what works, that could be what works for them personally as readers as well as writers, just as much as what works for the market, and when I say them, I also mean us, because we are the market, even during those times when we are not that part of the market whose tastes are being most often served.