Isn't it the case that kickstarter isn't necessarily a store? Many projects explicitly guarantee that you will receive a certain item, and some are even already manufacturing and selling the items but appear to just be using kickstarter because of its prominence and trendiness.

I'm sure kickstarter isn't liable even for the projects that explicitly promise delivery, so it's still not quite a store in those cases, but I assume that kickstarter doesn't prohibit projects from offering actual preorders.