The entire point of writing is escapism, to not be bound by reality, to escape it (hence escapism); by enforcing real-life rules, you are tying writing to the laws of reality, making it no longer escapism or a chance to do what reality makes impossible. Some people even use writing as a form of therapy, and therapists even support this method of self-help. Some people just want to put themselves in the position of being in a childhood they wished they had, but never did. You are removing all of this by enforcing this rule; there is nothing gained, only lost, as anyone not wanting to have 15-year-old-or-under characters don't have to use them, and never did, with or without this rule.
If you're banning this, you should also ban furries, rape, hardcore BDSM... The list goes on. Fairies and magic should be banned, too, since fantasy isn't real. As for age of consent, another particular roleplaying site allows as young as 13, is also based in US, and has had FBI scrutinise their site when a real predator was on there, who said there is no law in any US state which forbids anything like writing as underage characters and their site was completely fine and legal. If you'd like to know which one, I'll tell you in private, since it's apparently a rule to not post other sites here (why?).
I can't agree with any of this, and never will be able to, so my Supporter subscription has been terminated, and this site will never see another cent from me. This is all I have to say on the matter, so you won't see me again in this thread. This is both disappointing and infuriating, but it's clear the staff have made a decision and are going against what half of the members here are discussing, so I'll not waste any more of my time or energy here.