Gaming is a social past time now, usurping the roles once occupied by things such as hanging out at the mall or going to the movies. When I grew up, my favourite hobby was just on its way toward general acceptance (I was ten when FFVII came out...), but wasn't quite there. To this day, I still have people look at me oddly when I shout “Objection” at the conclusion to an Ace Attorney game.
Don't get me wrong, I have a PSN account and Xbox Live Gold, and quite enjoy talking to people in a party while playing a game. I just never play games with the people I'm talking to. In fact, the last multi-player game I played was Brawl.
Many games companies will tack on a last minute multi-player component to a game to help it sell well, be it competitive or co-op: some work well and some fail horribly. As much as I want to blame Halo and the like, there isn't anything wrong with being able to play a game with other people, provided it's done well. I just don't want to.
I grew up playing games alone. To be honest, there was the odd bout of co-op in Sonic 2 & 3, and whenever my brother brought his friends over we would play Goldeneye or Super Smash Brothers. Generally, though, it was a singular experience for me. I wouldn't even trade my Pokemon because I got too attached to them... still do, sometimes. (Naming Pokemon after Ace Attorney characters is unnecessarily awesome, by the way.)
The biggest thing, though, is that a lot of games I enjoy are single-player affairs. RPGs (no, I will never touch an MMO. I grind enough as it is), Adventure games, rogue-likes, etc. I've never been into the traditional competitive genres of fighting or sports games, and I only just started with FPS games in the last couple of years. A quick scan of my gaming shelves reveal maybe ten games with an interactive multi-player aspect (time trials are not being counted), and ten times as many that do not.
With the rise of gaming amongst the general populace and the internet bringing gamers together, people are playing with each other around the world and forming friendships with people they otherwise never would have met. And I continue to toil away at the grind in a voluntary isolation. There is no need for a 2P in Cross Edge or Touch Detective. And I'm content with that.