It's called evolution.
Yes, skimfree TGPs are cleaner and tend to make more money per surfer... but these days it's far easier to grow a skimming TGP and make up for it with volume.
I'll go out on a limb here and give you some real figures. When my (skimming) TGP was at 100k, I was making approximately $US2000 per month from signups off hosted galleries. I'm sure plenty of you make more than this, but the beauty of this site is that it is nearly fully automated. Both trading and thumb rotation are handled by scripts. There is very little human intervention required, maybe 30 mins work average per day.
This is the future of TGPs. Bang in a thousand hosted gallery URLs and suitable thumbs, configure scripts, then let them do most of the work.