This allows a company to rip many of its customers off with little or no repercussions. It's not really about the money.
I suppose at some future time if Steam did decide ripping people off was in their best interest it could, at least briefly. However I think Steam at present is smart enough not to do so.
With the disaster that was the RAGE release, a lot of people had a non-working product in their library. Some were willing to wait out driver releases and some just wanted their money back. From everything I read on the forums, it sounded like people were quite easily able to get refunded for their purchases (I'm assuming the game is somehow removed from their library, at least that's how it worked when I asked for a refund from Impulse). I think in most cases, Steam is willing to work with users.
Perhaps in some hypothetical future Steam will turn to the dark side and this will matter, but it doesn't seem likely.