I am suggested that they were buried to indicate the passing of generations one after the other. But that is a hypothesis.
"Five thousand years later you have the Sumerians buying ritual sites and temples once they were 'de-activated'. It may be that some of them fell out of astronomical alignment as the site was in use long enough for that to happen. "
That's interesting, do you have some of examples from the Sumerians. That could be a connection.
"You have to look really hard to find examples in history of people caring about distant generations."
See my answer to your first statement. I think they were passing skills and information to their next generation.