I can't afford to go to restaurants all the time, and I don't like bars or the mall.
I'm shy and I don't do well around strangers, and even when I do meet new people 99% of the time we don't have much in common, so it feels like a waste of time.
I'd much rather surf the web... at least there I'm learning stuff, and I can communicate with people who I actually have something in common with.