I'm not sure that "greed" has anything to do with this. If I had $1 million in the bank to fund a game, or I could get other people to pay for it via Kickstarter, I would do the latter. Not because I'm greedy, but because it makes more sense to get other people to pay for something than for me to pay for it. It's not like it's a charity where they get nothing in return. It's also good publicity for the game.
If you pledge $15, you get the original Defense Grid, the Containment DLC when it's ready, any other Defense Grid DLC created with money from donations, plus Defense Grid 2. I think that's a good proposition for gamers and it reduces risk for the devs.
You might get those things, nothing is guaranteed. At the moment you get the original, which I expect the majority pledging already have.