The value prop is that dumbpipe handles encryption, reconnection, UPnP, hole punching, relays, etc. It's not something I could easily replicate with netcat, for example.
In practice, the "ticket" provided by dumbpipe contains your machine's IP and port information. So I believe two machines could connect without any need for discovery infra, in situations that use tickets. (And have UPnP enabled or something.)
Why combine only two things? I like to invite my dates to my work Zooms so they can see how professional I am / my sandwich skills. When I meet up with my friends, we online shop at macys.com while on the treadmill. It's just more convenient.