THe trash you see is from independant idiots. I have been with several mazama groups out there and we always take great care to leave no trash.
It is not just climbers that use that place by the way. ATVr's, Horse back riders and the scary traveling randoms.
It is a free public camp ground. It is skull hollow what did you expect?? Sad to say but people as a general don't take care of things that are free. Take and Take is the rule.
So did you pick up any trash while you are out there?