People want to make choices that are positive. Sure, it's fun to go around in inFamous and destroy people and cars to your hearts desire, but in places where you're the "hero" and "protagonist" of a game, you're sort of expected to make "heroic" and "good" decisions. If you don't it kind of feels wrong. It feels out of character. You're trumpeting to the world I AM AN ENORMOUS ASS, something you don't want anybody you're going to root for, going to grow attached to over a long period of time, to say, or to be. And, by extension, if anybody around you calls you a senseless ass, it's also jarring.
That, and there's a collective sense that being good is "harder" because it involves restraint, and there's a mindset that doing the more difficult thing will be more rewarding, both in having fun with the game and in actual upgrades.
Personally, I always play "good" on my first playthroughs, because more or less I have a "good" outlook on general human interaction.