My biggest reason is that I just play too many games that don't really do much if any multiplayer. Perhaps if I knew more people that I could hook up with I'd pick up something like L4D or L4D2 or even one of the Modern Warfare games...Even then I don't know if I'd spend the kind of time on XBOX Live to make it worth having.
Meh I've had little time and yet i still play it. Most games are enjoyable in multiplayer over just playing it alone. It's why i pay for xbox live and still get 1 player only game cause it's fun ^^ Mw2 bleh get used to seeing noobs. L4D2 better to go in as a team of four into verses.