I've linked this about 72671791624 times in this thread now. Here it is again:
http://www.escapistmagazine.com/art...tra-punctuation/9967-Hating-Multiplayer-Creep
So....
1. People don't like social interaction with others.
2. People do like social interaction with others, but not online where they can't speak face to face.
3. People love social interaction, online or offline, but don't want it to cut into their gaming time as they prefer to play alone.
4. People enjoy playing for immersion and roleplay, and running into people who pointlessly drag you out of your game for "no reason":
utterly ruin that immersion.
5. People don't want to be responsible for someone elses gaming enjoyment by playing multiplayer.
6. People don't want their own enjoyment of a game to be in any way dependent upon other people playing.
I understand all of these, but they mostly seem to come down to risk.
You don't want to risk certain kinds of encounter/interaction so you choose a different mode to avoid them.