Right, and how am I supposed to have an impromptu LAN party on the couch, with zero planning, at my house or apartment, with my friends/siblings, without having to perform extensive setup and then spending hours on network troubleshooting?
The problem with PCs is that they're large, difficult to move about, difficult to network, and not everyone has one. Plus you need a crapload of space, time, and tolerance for frustration to hold a LAN party; plus you need the good graces of your apartment/housemates.
You need only one console, it's already set up, and it's guaranteed to work right away if I want to play with my brother or ladyfriend or whatever.
In theory it's a great idea. In practice it only works for the dedicated: the ubernerds. Gaming isn't the exclusive domain of that subculture any more.
And even if you do have a LAN party, you can use consoles instead, and get four times as many players in for the same amount of effort. Consoles take the cake on this front.
EDIT: And I used to LAN heavily, so I'm plenty experienced on that front, but it's just a huge pain in the ass.