I have - or rather, have NOT evidence that some families simply are not interested in their ancestry!
My OH simply didn't know anything about his ancestry, despite most of them being in the town he was brought up in. Until I started digging, he knew his mother's maiden name, and her father's name, the name of his grandmother on the paternal side, and that that side of the family had come from another town.... and that was it! None of them seemed to have been close, or to meet up at family events.
I set off armed with only the casual comment from my mother in Law, some years ago, that her mother was called Tabitha, and had the same birthday as I had! No certificates, photos or family documents survived after said M in L had a good clear-out a few years before she died, not even pics of my OH as a child or youngster. The only one we had was one I'd borrowed from her, years before, and forgotten to return.
I found the marriage of his maternal grandparents from that, and set off. On the other side I did pretty much the same, but it was harder because that'd been an R.C. marriage
From that, amazingly, I managed to dig most of them up, so it's not impossible!