Yeah, but humans do lots of stuff just for fun too.

It was a serious question. I see this "probably ritual" a lot when reading about old things. I get the feeling that this comes from some older Hobbsian "brutish and short" view of how people lived. Like "since they where not as advanced and smart as us the must have been half starved all the time and coudn't possibly have a ball game just for the hell of it"