Nice that you completely ignored how much of a huge pain in the ass it is to take a computer down, put it in a car or whathaveyou and move it to a friend's place.
I didn't ignore it, I just consider it irrelevant to the actual game-playing experience. Also, if you have a dedicated LAN machine, it really isn't all that hard to take apart and set up because LAN machines are generally small and you only use them at LAN parties.
Not to mention those days we brought over a second TV and second XBOX and had 12 people sitting around doing 4x4 Halo (we obviously had to switch off.) There goes any fear of screen watching - each TV had one entire team!
Yes, with each person staring at a tiny portion of each TV screen. Sounds awesome!
Can't really do that with PCs. All we needed were two couches, two tables and four outlets. For 8 people.
Again, if you have to divide a screen four-ways, the gameplay experience is pretty much ruined. I'll gladly put in the effort needed to participate in a LAN party rather than settle for the easier but compromised experience of playing split-screen.