I wonder if play isn’t more of a constant amongst people who suffer from poverty and hence not so much a luxury as a matter of survival?

Everywhere I’ve got where there is a lot of poverty there tends to be a lot of active participation in sports as an outlet for boredom without requiring much in resources.

The popularity of soccer around the world comes to mind.

Also, the archetype of the joker, the trickster, the storyteller. Many cultures around the world have oral traditions and stories that aren’t told through rote description but in an entertaining constantly evolving way.

This requires an amount of play on the part of the storyteller and the audience.

Then you have your joker, always making light of the world, turning everything on its head.

I simply point this out because your response seems to dismiss play as a guilty luxury of opulence when I see it as the most basic resource we have.

I’ve seen starving children play. It’s something you can do when all else is gone.

If we have a guilty reaction to it though it’s more likely to stay in the shadows of our life and psyche while we worry about the world’s inequality. If the main theory of the OP holds true we will be worrying about that inequality in a fixed way that doesn’t lead to innovation because we haven’t made room to play with the idea.