>>7488
If I had to take a stab at it I would say that it has to do something with the 3 depictions of werewolves sort of falling into the gaps, so to speak.
>type 1: folklore werewolves
Basically just a wolf. Has human intelligence and cunning, may or may not have human mentality.
This one just trips the bestiality switch for too many people.
>type 2: classic Hollywood werewolves
Wolfmen. With varying degree of hairiness.
I'm almost sure there were some erotic wolfman pulps back in the day but the problem with this type is that by the mid to late 70s this kind of werewolf had fallen into complete parody, even more so than how the other classic movie monsters had, and unlike them it never really recovered.
>type 3: "modern" Hollywood werewolves
Hybrids. Think Howling, AAWiL, Dog Soldiers, etc.
Once again these are animistic enough that they'll fall into being classed as bestiality. Additionally they're depicted as much more horrific than either of the two previous types so that also ends up being a limiting factor.