I agree wholeheartedly. I personally hate optical media, and see no reason why CD drives exist (for those with broadband), save installing the occasional OS. If a game that I want appears on Steam or XBLA, I'll pay for it in a second. No CDs in drives to worry about, and I can just sit back and do other things while it downloads, which to me is the perfect solution. If I notice a game that I want, and god forbid I have to go out of my way to drive and get it, chances are I'll take the other route. The reason I'm so inclined towards downloadable content is because I'm lazy and impatient. Ideally, here is my process for buying a game:
1. Hear about it through some news aggregate, forum, colleague, etc.
2. Go read a pre/review online, see what the general consensus about it is.
3. If I like the idea, grab the demo.
4. I'm sold, let me go download it and play.
Personally this is why I prefer Live to Steam. For the trial, you download the whole game - once you've finished the demo, it simply asks you to pay and unlock the full thing, and you can just continue playing as if you bought it from the start. Simple, painless, and most importantly, quick.