Check out Bitbang:

http://github.com/richlegrand/bitbang-cli

I've been using it and it certainly has the potential. I signed up for Cloudflare's TURN server which you use with bitbang and it gets you 1TB free data transfer per month.

That's because they're actually not "sending files to another". A hairpin service has to be provided for double NATed scenarios and a rendezvous service has to be provided for all cases. There's no magic about WebRTC that makes it actually p2p.