Cause the NSA ain't providing code, bandwidth, or servers to scale the system to millions of users. Google and Facebook have the knowledge and resources to actually do it, if they want.
But yeah, its a pretty dumb hope. They don't want you to have any anonymity as it is.
I think it would be cool if some one were to design a cryptocurrency wherein the proof of work was somehow related to the number of connections proxies. So mining would actually be providing anonymity to those who needed it and their would be an incentive to provide service. However that trick of providing indisputable proof of work, while not reveling the traffic or inbound/outbound connections might be a bit tricky to get right.