Three conditions for creativity need to exist: purpose, restriction, and action. You can have purpose and restriction, but if there is no action, you cannot be creative. That is where play comes in. Play delivers action.
Play and creativity share many common characteristics, the least of which is the lessening of consequence. The fear of consequence inhibits your ability to risk, and without risk, novelty is dead on arrival. Play can help circumvent consequence and train you to be fearless in your ideation.