What Microsoft and Sony don't seem to quite get (Although, I think Sony's a little clearer on the concept this time around) is that you can't put Steam in a brick-and-mortar store. There are expectations that come from buying a physical object. When I spend $5 on a whim to try out an indie game on Steam, I know it's buyer-beware. If I don't like it, that $5 is gone, and I'm willing to spend that money on that risk. When I walk into a store and pay $60 for a game, I'm buying an OBJECT that I expect to be able to loan and sell and retain value after my purchase.
If I'm going to be buying a physical representation of a digital object, then I expect the same pricing as digital game files. If I can't go to Gamestop and get a "Deal of the Day" for $5-$10 like I do on Steam, it's going to be very hard to sell me that game.