They don't make demos because dev knows they make average crappy games in the industry, so producers push the advertising and merchandising to impact the public, then they make their benefits and they're happy.

There's a huge amount of game I "pirated" that I wanted to buy at first, well I'm happy I never did, most of those games got me bored after a couple of hours. Those who deserve to be paid for, I do it during steam sales because I'm a poor mozerfucker. xD