I think part of it is that there's no real venue for customers to express their satisfaction to other prospective customers. If I find a store relatively well-laid-out, convenient, and friendly, I don't have a lot of opportunities to evangelize that store, even if I want to, because my legitimate actual real customer opinion gets crowded out by and blends in with astro-turfers. Sure I can talk it up to my friends, but that's not really a common topic of conversation.
