Why is it silly? There are already other threads on this site describing in detail why a great number of people will not purchase games through an online client like Steam.
If a game developer considers that population base acceptable losses for the sale of their game....well, that I think is silly.
As to your comment about retail sales; it's conjecture. If people decide not to buy games online, I'll bet you game developers will switch back to retail in a heartbeat.
You are missing his point. There is barely any retail PC gaming presence at all today as it is. Most PC gaming sections in stores are half WoW, nearly half Sims and a couple other big titles. That's it. In 2 years or less there will be NO PC gaming presence at retail. It's dead Jim, believe it. It's basically already dead.
Digital distribution is pretty much it for PC gaming already and soon it will be all there is. So get used to it. Be it Steam, Gog, GS or direct from the publisher it's going to be your only choice if it isn't already.
And as pointed out there are so many good games out there right now that just wouldn't exist if not for Steam or digital distribution. You think an excellent game like Defense Grid would sell at retail. Or Legends of Grimrock? Heck no. Even 10 years ago see the struggles of Stardock, one of the bigger Indies at the time (and still is) trying to get their games at retail let alone selling them.
It's just the reality we live in.
And I don't doubt the next gen consoles will go more toward digital distribution as well. It will be a transition generation and the generation after that will probably be digital only. 10 years from now I don't think there will be any physical games sold at retail anymore, even console.