Not sure I can agree. Years ago we had a kind of monopoly from STEAM. The competition was not very fierce. Key sites weren't very used. Now you even have a lot of different FRM (Origin, UPlay) and a lot of programs (there is playfire, Capsule and Desura, apart from the standard Orgin and UPlay). Also, before sales were kind of a big deal. People used to wait ages for deals. Now you have pretty much year round sales. GMG always have a code or two knocking about, and many websites have the daily things and stuff. This means that other websites reduce their prices before the STEAM sale comes along (which ties in to the 'you have all the games you want' part).
"Years ago" sure, but not two years ago. GMG, Gamersgate, Gamefly, Origin and Uplay (as well as all the dodgy/not-dodgy CD key sellers) have all been around for at least a few years now.
Regarding your second point....I don't know. I think all the games I bought have re-appeared at the same price or lower (if CS:GO won't get a 75% off, that will be a first for me).
I bought the GTA Complete Pack for £4.99 a few years back from Steam, it's never gone that cheap since (that I've seen, anyway).