speaking from a purely economic point of view:
people decide on an individual basis how to allocate their resources; always expecting a return. things like solar roadways, which would be super-awesome if they could somehow pull through well, don't offer guaranteed returns to the specific individual. it stands to reason that, if you can put a relatively insignificant amount of disposable income towards something that you can enjoy and share with others, and fairly confidently expect that that investment will yield the anticipated return, it is a worthwhile allocation of money. bonus points if you already know about the creators and want to support them.
also just the fact that people value different things and maybe some guy felt like playing some dumb card game about cats iunno w/e