because those small businesses aren't a brand the customer associates themselves with.

people who brand shop often brand-identify, and their self-worth/image derives from purchasing the brand's products. they won't go to another place because that would mean they are a different person, they are a SB person, not a third party person, not dunkin donuts person, etc.

just because you don't think that way, doesn't mean there aren't millions and millions of folks who do. just like the fact you might not use face book, but there are 3 billion people using facebook.