> If you use it to talk to friends, you'll presumably have your computer on when you want to use it yourself anyway.

I tried this in the past but it didn't work. Now if your friends want to play you need to start the server for them. What if you're not at home? You basically end up making your pc a 24/7 server. Or you need to coordinate so that someone else runs the server in those cases, but that ends up creating more confusion. And let's not start talking about port forwarding issues...

All these issues are solvable, but they add so much friction when all you want to do is play with some friends.