Yeah, I can see that.
But seriously, how much "incest" does the average family tree really have? And I'm drawing the line at great-grandparents, anything less than that is unrelated imo.
Royals were doing multiple generations of first-degree incest, that's on a completely different level from normal people.
Like I said, royals aren't normal people. See the fabled family tree of the Ptolemaic dynasty:
But that only works if you have a family fortune to protect. Normal people would rather spread their children around and increase their chances of survival.