I don't think they have the best interests of the populous in mind at all. It is all about pandering to the lobbyists, who give them money and incentives.
Now days, you need to have a way to try games before buying them. Here are my reasons/opinions:
1- Game demos really suck and don't really give you an accurate idea of how the game will actually play as you progress. For example, I played the demo of Reckoning last night. I couldn't change the resolution to what I use on my monitor. The textures are low resolution, to make the demo file size smaller, and able to play on more machines. After the tutorial, I got a message saying that I can explore the game for 45 minutes before the demo ends. There isn't much you can do in 45 minutes in that game. Walking around and getting aggroed by various mobs will take 90% of that time.
2- Return policies of games suck. If you buy a game, and open it, you can only return/replace the game for a copy of the same title. You can't return a game, because you fell for all of the advertising hype, and the game ends up being buggy garbage.
3- Renting a game is becoming a non-option due to the fact that once a code is used, it can not be used again, so you will miss out on features. Less games are available for rent. A lot of studios seem to be cracking down on rentals because it cuts down on sales revenue.
I admit that I will download a game and play a decent chunk of it. If I like it, I will surely buy it, as evidenced by my shelves full of games, and hard drive space being taken up by Direct-2-Drive and Steam games. If the game is buggy crap, like Rage, for example, or just thrown together with a movie title slapped on it, I do not buy it and am happy that I didn't blow $60.
I believe that good work should be rewarded with a purchase so that the good work continues and the studio is able to release more titles in the future.