When I was an admin of an IRC network we regularly reported large scale DDoS attacks to an FBI agent assigned to us. He didn't care. Some of those attacks took the network down for a while and resulted in many users moving to other networks. In at least two cases we even figured out the identity, address, and phone numbers of the people doing it and there was no movement on it.

Then one day one of the people we had the identity of boasted on how he had briefly brought down the website of one of the democratic primary candidates. We forwarded that information and our case was reassigned to another agent and the person was arrested immediately. I absolutely think it's true that the US government is only interested in protecting established and powerful figures. I suspect the reason is career driven - defending the little guys isn't glamorous and probably has no promotion impact.