Anyone can ask for donations but why not offer a reward people will actually use and love? How many times a week do you think these same people are being solicited to support other causes? The reality is, people are busy and their bandwidth to help is limited.
Whether you agree with it or not, our economy is currently built on people buying things - lots of things. And since people already buy things, at an amazing rate, why not help them do some good at the same time. For some reason rewarding supporters with something that they would actually want to buy, up to this point has almost been an oxymoron.