The issue is that they were still in their uniforms and on the ice. Therefore it still is part of the Olympics. It's not that much of a stretch to see why they're just a little concerned about it. Had it occurred in the locker room I doubt the IOC would care.
However, it seems as if it's not that big of a deal any more:
Smoke, but not a lot of fire to Canadian women's hockey celebration, LA Times
"I would say to characterize it as an investigation would be wrong," IOC spokesperson Mark Adams said at a morning briefing Friday. "We are just writing them a letter just to find out a few more details."
He maintained that the scrutiny was coming not from the IOC but the media. That seemed partially correct. The IOC didn't weigh in, apparently, until asked about it by the Associated Press. Still, an IOC official did use the words "investigate the actions" in the AP report Thursday night.
"To be honest, I think people are in search of a story that doesn't exist," Adams said. "There were pictures all over the front pages this morning. I guess we'll just be asking for some clarifications and explanation of what occurred."
Later, it sounded as though the apology served as sufficient damage control.
"I think if you read the statement from the athletes, they clearly knew they had gone out of bounds and they said it was inappropriate and they apologized for any embarrassment, so I think it's pretty clear they know they overstepped the bounds," Adams said.
In other news about Canadians and drinking, this from Phoenix, AZ:
"Drunk Canadian" Begs Cops at Sky Harbor Airport to "Taser" Him, Tries to Fight a Woman, and Breaks a Cop's Ankle; Oh, Yeah, It's on Youtube
Phoenix New Times, Valley Fever Blog
By James King in Another Stupid Criminal Story Mon., Feb. 22 2010