Because throughout his career, he made d*mn sure than any woman who got some sort of meaningful "come up" or career boost off of him were either biracial, Latina and/or White women (including White lesbians like Wendy and Lisa)! In other words, anything except full-Black women. And certainly not dark-skinned full-Black women.
The only difference between Prince and the modern day Black males who erase Black women is that Prince was always silent about it. He didn't publicly say anything that was anti-BW (he wasn't doing a lot of public talking in general). But his DECADES-LONG ACTIONS said everything that needed to be said.
As a college girl, once I saw that Prince was falsely portraying himself as biracial when he was NOT (in his movie Purple Rain), and took note of how colorstruck and racist he was in terms of the women he surrounded himself with, I was done with him. I'll note that according to some of the accounts I've seen over the past couple of days, he also discriminated against dark-skinned Black men, such as Alexander O'Neal (who is currently a drug addict, but I don't know if he was an addict back in that day). [Edited to add: Not that I care about Alexander O'Neal. I don't. My point is that there was an anti-Black pattern to Prince's hiring and promotional practices.]
Nevertheless, everyone's mileage will vary. I'm just saying why I'm not broken up over Prince's passing.
Various receipts in these Lipstick Alley threads: