Because you're funding a project that may or may not work out. The whole point of crowdfunding is supposed to be, "You give us money to develop an idea, and you might get a reward in return", not, "I'm paying you $35 for an order that includes a bumper sticker and a t-shirt with your logo on it." It's less like your carpenter example, and more like a VC firm dumping money into a startup.
It's supposed to be speculative investment. Whether or not Kickstarter and others have decided to backpedal and pretend they have some kind of legal precedent for holding project owners to their word, in order to make their own business seem more legitimate than it is, is another story.
It's supposed to be speculative investment. Whether or not Kickstarter and others have decided to backpedal and pretend they have some kind of legal precedent for holding project owners to their word, in order to make their own business seem more legitimate than it is, is another story.