Of course they will sell the game, that doesn't stop it from requiring me to run the Steam client to play it, download it, and update it. GFWL is a little different. It only runs when the game runs, it doesn't force updates on me, I don't have to log in to it if I dont want to. I've got a few GFWL games like Fallout 3 and Viva Pinata and the most I ever saw of GFWL was a little "bloop" sound telling me to hit the Home key to open it. Which I never did.
This isn't about who I hand my money to, this is about who ultimately holds the leash for my game.