If we dial into any number of our "higher level behaviors", you can often go all the way back to "survival". Play is an important part of skill acquisition, and the easiest way to incentivize it is to make it "fun". Naturally, having fun as an evolved trait will lead to behaviors that don't necessarily have an obvious survival benefit.

I'd be more surprised to see a mammal that doesn't at all engage in behaviors purely out of enjoyment.