Once again, our imagination is put to good use when we decide to make something.
We primarily learn by listening, watching and doing. While listening and watching are a great way to gain knowledge and get great ideas, the real benefit comes in actually doing. In addition to imagination, actually doing helps develop those senses of sight and touch. In this way, children learn, in very simple form, how to analyse problems and how to solve them.
One of the other great benefits of doing is that it teaches persistence - a critical habit to develop. Success in anything rarely comes about without persistence and the sooner we develop this habit the easier it will be. We don't want to raise a generation of quitters!
They may not, probably won't, get it perfect the first time, but if they really want to make that sail boat or draw that great picture, then they will try again until they get what they want.
Winning a prize for the best creation ever known to man, is not the name of the game. It's that boost of self esteem, that sense of satisfaction of creating something truly unique, that's the real prize.