Of course if a store is just plain cheaper and over all quality wise better, it it's not that important that it looks hideous and abandoned. But to some people it matters. And if two stores provide the same product at the same price, I think I'll prefer the one that looks nicer.

It doesn't decide everything, but it's pretty certainly a factor (although Amazon must have determined that it's a small one to them, as they are still micro-optimizing for other page-related aspects like loading speed).