I don't think there is really any reason to assume that. Marrying your cousins to keep the line pure and keep wealth and power centralized also happened a lot (and I mean a lot) amongst Muggle nobility and those nobles obviously didn't have access to Amortentia.

@LectorMagnificus Well, yes but there had to be other dissenters in the Gaunt family like Isolt Sayre and Merope Gaunt they couldn't all be okay with the incestual relations.

That would depend on how much power they would have had, magical or otherwise. It was clear in HBP that Merope, while being magically powerful enough to seduce Tom Riddle, was being completely dominated by her father and brother. Furthermore, if you grow up being told that there is no problem with marrying your cousins and that it is expected of you, I don't think many would just go against that, though there would be exceptions, of course.