Coming from an ONM interview...

"This is a way for people to share their experiences. It's a social thing, something potentially endless that they can play over and over again. We are releasing new challenges every day and every week, so the competition is always really exciting." - Michel Ancel
"When we released the demos last year we saw how people were competing by posting YouTube videos of their times in various levels. This is really our chance to facilitate some of the competition out there and see who's the best. It's also a way fore everyone who was disappointed about having to wait to play a part of the game now." - Senior Game Manager Michael Micholic
Micholic said that the idea to release this content early was spurred on by the delay of Rayman Legends.