What milf said - plus there has to be a cut off point somewhere. If you can argue for 17, you can argue for 16 - and then 15 and then 14 and some girls are phyiscally 'mature' as young as 11. Same for boys - puberty has no hard and fast rules - the Feds do.

The 'cut off point' for pictures and sexual discussion on this site is 18 - It isn't open for discussion, which seems to suit the vast majority of members here just fine.