Helmet Stickers

What ever happened to all of the helmet stickers on the backs of the helmets for "rewards"?  Ohio State still has those asteriks that are supposed to be Buckeyes.  Michigan used to have little footballs and I believe they had a Wolverine stamped on it too.  Maybe I'm making that up in my mind, but I remember by the Ohio State game the starters would have tons of those footballs up the back and sides of the helmets. 

I'm sure this was covered years ago when they stopped... but why did they stop?  Just to keep a clean look?