I can say with confidence that I am much more willing to drop $5 on a game via Steam than <random 3rd party site>. Aside from the obvious "is this a scam" aspects, Steam means that I will have the game even when the dev goes under in 5 years, that my save states will be backed up, and that at least some of the reviews might not be faked.
That 30% might be painful, but at the same time Steam provides a LOT of utility to the buyer.
That 30% might be painful, but at the same time Steam provides a LOT of utility to the buyer.