Why do most black women refuse or won’t date outside of their race?

I have a friend that I’ve known since 6th grade. She’s funny, intelligent, beautiful, witty and kindhearted. Great friends, family but no boyfriend. She’s dated a while back but she only dates black men. I understand most people prefer their own race but as long as someone treats them right, why should race matter?
there’s this guy that absolutely likes her. I mean he really REALLY likes her but I don’t think she sees that he likes her. They’ve known each other since childhood and he even admitted that he would always follow her around when he first laid eyes on her, always called her his Valentine and asks her out numerous times (middle school and high school) but she had always turned him down. She went with him twice (8th grade dance and junior/senior prom in 11th grade). I even explained to her that it’s so OBVIOUS that he likes her. Why doesn’t she give him a chance? He won’t give other women a chance but her. He was never interested in the slim/fit or gorgeous girls. Only her.
She told me she rather keep the friendship than to date him and make things awkward. She said honestly that she preferred to date black guys or men or color, nothing against white guys. He’s a white man and I can tell he is very attracted to her. I’ve seen the way he looks at her. Even on trips I’ve cough him staring at her. She keeps saying they’re just friends. What’s wrong with a white man liking a black woman? Even her friends and her parents can tell he has had a crush on her.

Updates
6 mo
She said always crushes on the black jocks or good looking black men, but they won’t look her way and one said he can’t see himself dating a chubby/fat overweight tall girl and she should date someone her own league.
She told me she said I should date fat chubby guys, like that guy (her guy friend). Chubbies attract each other.
Why do most black women refuse or won’t date outside of their race?
Post Opinion