Yes there is a component of tribalism. But I think to an extent wealthy/powerful families like the Windsors for example act like their own tribe. I think of it more like "localism taken to its logical conclusion"

Any organization is going to have the problem you describe as people inheriting a birthright will value it less than the person who created it. The hope would be that it would be less likely and take longer to decay than a government institution where people don't have skin in the game.