Btw Rudolf Steiner (of Waldorf School fame) would also outlaw ball games, at least soccer. After all, the ball could be mistaken for a head and it could train kids to kick heads.
1) they learn to have fun without the need to feel superiour (ball games need some supervision in that regard though)
2) they learn emotional intelligence, especially for activities that require collaboration (surfing not so much though)
people tend to miss, that in the early years many inner brain functions and predispositions, especially emotional regulation get tuned for the rest of the life...
And it can also train emotional intelligence to win or lose gracefully in games, and try again.
What will your kids do when they encounter somebody who "feels superior" later in life? Like an actual superior, perhaps?