There are far more female masseuses than male. Most males feel that they really need a chaperone in the room if they work on a female, too.
Many men, when having a massage, expect to have some sort of sexual undertone to the service, even if they don't get stimulated or ejaculate. Not all men, but many.
Personally, I'm capable of enjoying a massage from either sex, without having a sexual component to the experience, unless it's my husband doing it, in which case he's probably giving me a massage specifically to get me into the mood.