Survivorship bias probably if I had to guess. If Dad is bad enough to cut off like that, he's also bad enough to have had plenty of time to have alienated anyone who isn't also a shithead long before you got up the gumption to cut him off. There was also probably at least some part of it that comes down to their shitty behavior being shaped in part by the people around them.

This post is like some sort of multiverse nexus where other versions of me have congregated but it's just so many people's dads were somehow Like That