Honestly, as far as **** goes, it's all about the fantasy, right? Here's my theory (yeah, I should be working). There are three basic types:
1. Guy on guy: made for guys
2. Girl on guy: made for guys (I'm willing to bet that most girls don't fantasize about a guy getting off in their hair...really now).
3. Girl on girl: made for guys, however, more palatable to most women since women are more empathetic and can put themselves in the place of one of the characters. In lesbian ****, at least one woman looks like she's enjoying herself, unlike the other two main types.
Now when you get into fetishes and whatnot, that's a whole different story.
Nexa
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“It has always been the prerogative of children and half-wits to point out that the emperor has no clothes. But a half-wit remains a half-wit, and the emperor remains an emperor.â€
― Neil Gaiman, The Sandman, Vol. 9: The Kindly Ones