It's very simple: for bigger company piracy is more like a form of advertising, but for a small one it can actually hurt and kill the small guys.
If A is the set of people that've heard of your product sans piracy, and B is the people that've heard of it after piracy, then the gap between B' that pirates and B had better be smaller than the gap between A and B. That's likelier for a tiny producer than a huge one.
Big guys have free advertising from piracy, small guys are hurt from the same thing.
Edit: I guess we mis-understand each other -- I didn't mean VERY small guys, who may suffer from obscurity.