It all just boils down to "I must know what my teenage girl is doing." Which I get, and if you have a healthy open relationship with your teenage daughter (good luck!), good for you. But uncle or daddy might also be raping her, or planning to beat the shit out of her for daring to make Jesus cry. Or quite possibly she's just shy and scared for no good reason and you're wonderful parents who would happily help her. Establishing an age limit of 15 in a world where almost no 15-year-olds have real IDs and increasingly 17-year-olds don't either, puts up a huge access barrier to everybody. Fighting for a higher limit is worse.