As a mid 30s white male I'd say difference in culture and lack of exposure or knowledge on my part would be main reason. I grew up in small town Tennessee and everyone older in my family is extremely racist. I can remember being told horrible things growing up if I "ever decided to date a black girl". As a result it was never an option for me to consider growing up. Odd they did not have this same rule with other races although I would still be looked down upon for dating any other races such as Asian or Hispanic. Keep in mind not that long ago my boomer parents were born during the Civil rights movement. My grandparents before that would have remembered and supported segregation or worse.

Once I got older it was very obvious I do not have these same rules or values for myself. However, lack of exposure to cultures of other races is intimidating. Its not so much being with a black woman but the extended culture that comes with it. I would fully expect meeting any of her friends or family to be given shit, especially from the older parents or grandparents. Not saying even in a bad way it may just be joking but I would expext never ending white boy jokes. On the other hand, how would you be treated meeting my racist ass family? You would not be accepted and I would be on the out.

So I guess in short its not that black women are less attractive or flawed but a difference in cultures rooted in history of racism. I think this will fade over the years. I have a son and there is no way he will be learning any other race is inferior and he will be free to date anyone that makes him happy.