Labor faces a challenge in both chains and small entrepreneurs. On the one hand, there's an economy of scale for public protest against a chain. A boycott against the Gap can target many stores at once. Using social media it might even be possible for cashiers, say, across Walgreens city-wide to co-ordinate a job action. But the larger the corporation, the more resources it has, including greater mobility, which counterbalances the scale of public and the labor organizing. Stella D'Oro picked up and left NYC rather than negotiate. The garment industry left the country rather that pay a minimum wage and rent here. Retail chains can't leave, but they can hold out, and those employees that aren't unionized don't have much of a chance.
On the other hand, pickets and boycotts can succeed easily against a small business with a narrower profit margin. But it's rare to hold an action against a truly exploitative small owner because the profit margin is so narrow that the owner might have to close rather than capitulate, and closing the store puts the employees out of a job; everyone loses. So even the loudest activists somtimes have looked the other way. What made the fight against Jing Fong was the size of the restaurant.
A chain like 7-Eleven hires almost no one, so there are no benefits to the local economy to having them here. They're just easy, the way a Citibank on every corner is easy. And now you can even Citibike directly from it to 7-Eleven. Corporate heaven.