because YouTube has a lot more exposure than NHL.com (sadly).
youtube has more exposure than just about any website out there right now. there's no shame in being below it.
i still don't know if it's true that fan video's will be removed from youtube, but it's a shame if it's true. youtube may get more exposure than nhl.com, but i personally don't care. If i want highlights, there are plenty of places to go for them. If i want a replay of a goal from ten years ago or a collection of scott steven's biggest hits or a collection of highlights from some european prospect, it's not gonna be on NHL.com.
Maybe that stuff will still be on youtube, who knows. But if it's not, it's a huge waste of potential viral marketing.
Think about it : Say MLS signs a deal with youtube; are you gonna go to youtube to look for the highlights all of a sudden (assuming you aren't a fan) or are you gonna click on a link that says "New York vs Washington MLS Highlights"? Or are you more likely to click on a link that says "Freddy Adu Fantastic Goal Reel!!!".
Personally, it's an easy answer for me.