The one in Montreal was for the initiation week to the students that are in communications (media, and such) .. While the plan was in the making for a month they [the students] arrived to the university with only 2 hours to prepare the song and not having a clue what to do. They also had 2 takes, which they got perfectly on the 2nd try.
Apparently, the vid already made it to CNN, which is a big thing. It's free publicity for the school.
The other ones also are mostly Communication and Media assignments and stuff.
Technicall that's probably because what Flipmo said.
Also for fun, to do something people will like, showing the joy of being young etc.
To me it was a great show and personally I would love to be a part of something like this.
Just watching these videos makes me feel great.
It's somewhat like that video of a guy performing his fancy dance all over the world with local people.
edit: this:
[YOUTUBE]zlfKdbWwruY[/YOUTUBE]
I find things like these awesome and give huge props to people doing them.