Because the game is fun.
Some people don't care about the connections, they care about the game. Others are reverse and want to connect to someone whether it's just to that individual or it's to people who happen to play in the gaming atmosphere that they enjoy.
Thing is with cruelty, it's nothing when it relates to the game. Because unlike certain things in life, with a game, all you have to do is walk away. No one takes words truly serious when it's over a game, because it's a game. I cuss sometimes and talk trash even to grim because he's a noob. But you think he cares? He doesn't, and that's the mentality you need. And do I care that he doesn't care? Nope. Because it's meaningless in the end.
If UT died the next day and the servers shut down, I wouldn't look back twice. Sure there are some people I do like talking to but the only people I really do care about are my Clanmates (BLS), because we've been together for few years and we are beyond the standard clan criteria. Yet we will always remember that it was a game that brought us together.
As for you young one, you shouldn't take what happens here serious. Because everyone can see things more clear then you can over here.