In virtually all human cultures, as in those of other primates and mammals, sexuality is a status symbol. It's more visible for males, where bragging about sexual conquests is an obvious part of the culture. But it's just as important for females, where the largest focus is on sexual attractiveness as a means of establishing one's status within the group. Naturally, we are not monkeys exactly, and individuals often deviate so much you almost can't see the traces of this cultural element; but looking at larger groups, it's plain that it's there.
There are certainly groups where asexuality is a status symbol for solid, understandable reasons. For instance, a group which practices abstinence for religious or ethical reasons would naturally allow bragging about asexuality. But there's an obvious cause for it. It's innate in the intent of the group.
I've noticed that within the online community of players of multiplayer games, there's a curious variation on this cultural element. (Naturally I see this most in Lusternia since that's where I spend the most time, but I've seen it in other MUD and MOORPG communities, all of which cross-pollinate ideas anyway.) Players, when speaking of themselves in real life, are pretty near to the cultural average. However, when talking about sexuality as a possible element in the game worlds, or in any other part of the community (like ancillary cultural venues like a forum), bragging about one's aversion to sexuality serves as a nearly perfect analog to the opposite bragging done in the rest of life.
Clearly this is distinct in that they're not objecting to sex, but to the idea of sex being in the roleplay of the game world, and that's fundamentally a different thing. They're okay with sex, and just find it a bad thing within that context because of such things as the "every sexy 19-year-old girl is an overweight 50-year-old guy in real life."
And yet for as explicable as that difference is, it's striking how much the antisexual attitude perfectly parallels the way sexuality is used as a status symbol. There's precisely the same attitude of smug superiority when proclaiming one's aversion to sexuality as when people in other contexts brag about their sexuality. It's used in the same way to establish one's place within the pecking order; the more resolute you are about how abhorrent sex is, the more you can lord it over others. So striking is the parallel that it makes me wonder if the distinction, about how it's "not about sex" but about how it fits into the online setting, isn't just a veneer we place over a more primal attitude, inverted.
Of course, wherever sexuality is repressed, it tends to become more extreme and unrestrained. Once the basic act is deemed a perversion, it's no longer bound by the rules about what specific variations are considered perversions; there's no longer any reason not to go the next step. I wouldn't be surprised if, behind a significant number of those people who brag about their sexlessness in-game, there's an awful lot of sexuality that's going farther into unusuality than there would be in groups where sexuality itself was acceptable.