I think putting on make-up everyday kills the purpose. Whereas if you do it on special occasions or randomly when you are in the mood it does make you feel more special doesn't it? I feel that in their age it's more like a social programming they've received through various media and their friends who've been doing it before them. So they want to fit in and be like their idols on tv. I've got no problem with it though. It's their choice.
I had a friend in highschool who used to do her make-up as a stress relief. It does work lol.
Also I wanted to mention, a lot of products contain mercury and other harmful substances, you are absorbing it through your skin. In small quantities you won't notice but it adds up over the years. There are natural make-up alternatives. On a trip to morocco I've noticed they have some natural eyeliners made probably the same way as back in time in ancient egypt. :)
something like this one
http://www.hennaherbals.co.uk/hennaherbals/prod_1380536-Natural-Eyeliner-Sormeh-Black.html