Comment by AshleysBrain

UDP hole punching does not work with all types of NAT, e.g. symmetric NAT where a user can appear from the outside to be coming from multiple different IP addresses. (This makes the STUN server useless for telling the other peer where to connect.) Symmetric NAT is common in corporate networks, which I suppose is not the first place you'd find gamers (or you could just run LAN games with co-workers). I guess WebRTC is the first place you'd run in to networking problems with NAT outside of gaming, torrents and bitcoin - and is perhaps the first developer-accessible peer-to-peer tech which is obviously useful in the workplace.