I must admit, I feel a little insulted having my sexual orientation chalked up to fanservice.
Don't feel too insulted. Any kiss is a fan pleaser -- especially if it doesn't happen often or is between characters that fans follow. If they are rare enough, even a very innocent peck is, in a way, "fan service." Just think of all the TV shows that teased their audiences by suggesting a building relationship between main characters but denying them a simple kiss for a long time.
Having lesbians in a story doesn't make it fan service, but any time they "make out" is at least as much fan service as a straight couple making out. ;)
That said, I don't know why (many?) men are enthralled by lesbians. Or why (many?) teenage girls like to see effeminate guys making out... But since there are fanatical followings of such genres, some people will view ANY comic in those genres as "fan service." And some of them are. Just like some people draw in a more Japanese style because it's "popular." It is very insulting to think everyone does it for that reason. A lot of people draw that way because it is a style they genuinely enjoy -- having nothing at all to do with their "fans."