Crossdressers masturbate when dressed as women...
Since time immemorial, there have been men that got a sexual thrill from cross-dressing, and the presently accepted view of most experts in the field is that if cross-dressers go no further than putting on women's clothes and makeup and perhaps masturbate, that there is nothing to be concerned about.
The reason that so many crossdressers masturbate when dressed as women is because cross dressing has in the vast majority of cases, nothing to do with wanting to have sex with members of the same sex, i.e. homosexuality, and the opposite is more often than not, the case.
In the eyes of the cross-dresser, and in his imagination, he is the ideal woman, and along with that are the advantages that there is no fear of criticism or rejection, so for him, dressing up as a woman and masturbating is therefore a win win situation.