Hockey Night In Canada

So I'm watching Hockey on the CBC (it's nice, mindless entertainment to have on while doing other things). A fight breaks out. The refs pull back and even clean out some of the gear so that the fighters won't trip on it. They don't break it up, and the game is stopped entirely for the fight.

Why?

I mean, I get that hockey has a history of these fights, and I know the old joke that "I went to a fight and a hockey game broke out," but I just want to know why it's tolerated. You fight in baseball and you get tossed from the game. You fight in the NFL and your team loses yards. But in hockey everyone backs off and lets the players go at it. Why? And I never see a power play after a fight, either. Is there even a penalty for fighting? And what do the players gain from it? Status? A black eye? What? Maybe I've got a Canadian reader who can explain it to me...