Perhaps, human creation started with Adam, right? Historically werewolves were always male. English also sometimes makes use of the French-derived word loup-garou, from Old French leu("wolf") and "garoul" or "garulf" (a word of Germanic origin meaning "werewolf").

It was also easy to blame a werewolf or wolf man for murders, murderers would even blame there mental dysfunction on being a werewolf as probably a power trip for them. Pretending to be something there not and something that is feared was easier for them they knew this would frighten people more.

They used this as a form of cover for a excuse for there crimes. It was also hard for people back in the day to point the finger at a female and it was often believed that a werewolf was only male and would be the only one capable of committing a crime. Of course nothing was further from the truth. Werewolves can be male or female. And have nothing to do with murderers, it was just a cover for them.