An additional benefit would be that it offers more variety for people who wish to play the game more than once.
For instance, the first time I played KOTOR2, I specified that Revan was DS female... so Carth wasn't even mentioned at all.
Then the second time I mentioned Revan was LS female, and Carth was present all over the place, and I got to see that extra scene between him and Exile.
If I were to specify that Revan was male, then there would be some Bastila references. I think it just helps spice up the game, and encourages people to play more than once. Cause god knows if I wanted a repetitive RPG where the exact same thing kept happening, I'd just play Fable again. Sure, it was fun my first run through... but I'm SO never playing that game again.
I also agree on the point about isolating people who prefer a female Revan... I mean, yes, I'd still play, and no, I wouldn't be yelling "sexism!" from my soap box, but it would annoy me a little, just because I've come to see Revan as female, and I'd hate to see the whole Carth/Revan romance storyline come to an abrubt end just because somebody decided that Revan was male after all.
If they wanted Revan to be male, they should have just made him/her male in the first place and not given us the other option. That, I could live with better than having the storyline I'm used to suddenly be changed.