Skype won in part because other attempts at VoIP didn't work very well. There are lots of practical problems in just getting a p2p connection to work, there are

Skype won in part because other attempts at VoIP didn't work very well. There are lots of practical problems in just getting a p2p connection to work, there are often firewalls to route through. Trying to debug these is not helpful when you're just trying to find a way to talk with your mom.