[Symbiote]

If you have more than one device which needs similar external access, you won't have to use a non-standard port.

I have three devices at home which I'd like SSH access to. Because I only have IPv4, two of them aren't on port 22, and sometimes the non-default ports I've chosen are blocked by hotel Wifi etc.

Similarly, I'd like two different webservers to be available, but I can only have one on my single port 80.

For the more typical user, it can mean only one person playing a particular game etc.

[iggldiggl]

Yes, that is of course a benefit, but what I was trying to get at was that you'd still have to dig around within the router config, so it'd still not quite be the radically easy, absolutely hassle-free peer-to-peer communication world.