In all seriousness, I can see how snot rocketing isn't the most attractive thing in the world, but I can't understand why it would be unsanitary. If someone's licking the ground - or even putting their hands on the ground and then not washing them - they've got more problems than athlete snot.

To me, a handkerchief is unsanitary - putting a healthy culture medium on a matrix that'll keep it wet, jamming it in a pocket that isn't necessarily the cleanest but is kept nice and warm by your body heat, then putting it back onto your nose? Ewwwww.