i dunno about Alice but for Crysis 2, it wasn't EA's decision and was a conflict with Valve's policy on DLC's, therefore Valve took it off Steam. as for BF3 being Origin exclusive, i'll probably be buying it on disc instead of thru origin
From what I have seen steam seems to be a driving force in lowering the price of games. I got steam for team fortress. Then I got Global Agenda, then Alien Swarm, then MNC and so on.
Not to mention that Steam is really convenient. It's easy to find somebody on your friends list to play with, join their games with a few mouse-clicks, VoIP is available, chat, an overlay to access features you might need, screenshot manager... Except for video capturing software Steam offers almost anything you could wish for. Did I mention that it doesn't cost $60 per year either?