It's almost like the gender problem to me in some regards. I don't care, unless there is the [i]potential[/i] for it to get dark and/or steamy. Which is something I don't block from my interactions, so by default, roleplaying with me generally means you should be 18+, or I should have that impression so I can legally deny any shit happened.

While I doubt too many of them think of the legal aspect, that's still there. It's easier to throw off parents when you say "hey, he never told me he was 18, I didn't see it anywhere, and I had a rule that only adults were supposed to be in anyways". Liability is a bitch.

Sometimes it really is the stigma. While there are good 17 and under roleplayers, the truth is that many (well, just like adults) are simply posing as competent when they're really in a stage of growing out of metagaming and godmodding and the other shit that some people just don't want to deal with.

It's naive to assume 18+ stipulations will be more accurate than gender restrictions, but if I used it, I would consider liability, and on some level try and avoid having some forms of people younger than 18 contact me. I know it doesn't work at a fundamental level, but there are sometimes merits to such restrictions, and some people would honor the request. That said, I don't really care about player age and only want to have an idea before roleplaying if I can [i]assume[/i] my partner is above or below 18, in which case I can manipulate content accordingly and have a case to build in case some deranged parents try to call liability on me. I'll interact with above and below, and I may well have interacted with people below or far below without having a clear picture of it.

In short, liability is the main argument that I would consider valid. Comfort is naive, "I prefer to roleplay with x" is meant well but naive.

Doesn't help that the entire forum has, shall we say, "aged up" in terms of content that is more frequently seen in there.