The only people who can afford to shop exclusively at small businesses are people with a lot disposable income. Especially if you're talking clothes, those tend to be boutiques with designer labels and are extremely expensive.
It's actually almost a vicious cycle. Walmart and their ilk are almost the new factory jobs. We manufacture very little any more, so stores such as Walmart become the next best bet for employment for people with no higher education, besides restaurants. But add to that stores like that are the only affordable places for then to shop. Also, just think of how many people Walmart Kmart and target employ. Imagine what would happen if everybody boycotted them. Not that that's feasible considering the large amount if people that those places are the only affordable places to shop. But hypothetically, if nobody shopped there and we put them out of business just think what would happen to unemployment.