Same reason why these dark skin girls find happiness in the arms of white men too. I won't touch on that topic in here though
My friend was the blackest dude on the block and he's been called "black ass" "tar baby" "wesley snipes" by his own people.
The race that's being dominated tends to mimic the behavior of the dominant race, because who doesn't want to be dominant? Some black people have unfortunately adopted that shyt from white people, and are acting out against our own with that BS. Society has white standards of beauty, ever since they came here and destroyed the natives and put blacks to work and regarded them as subhuman. Unfortunately some black people aren't conscious enough to see the error in that behavior, and they're just perpetuating the problem.
Weak minded blacks will resort to this skin lightening shyt and general c00n/tom/bed wench behavior, because they've been hypnotized by society into thinking "white is right" and want to distance themselves from black people/things.