Earlier quoted context omitted.
Steam has Greenlight now, so you don't have to be "vetted" by Valve anymore. There are many other services already though that provide similar functionality, such as indie game stand, desura, etc. that have none of the restrictions you've mentioned as being a reason to not use Steam. So again, what makes this service compelling?
Greenlight is still a vetting process, just with a different mechanism. Suggesting that anyone can just get their game on Steam is flat out wrong. Really well made and polished games (see: Midnight Mansion from ActionSoft) fail to get noticed through either process all the time. I have nothing to do with this service but I find it definitely compelling. Indie Game Stand only features one new game every four days (so…
As the others pointed out, most of us don't want yet another game distribution service -- we already have a few.