Why is it when someone questions the beauty of black women?

Those that will usually post pics of black women either have caucasoid features and are mixed or one of the two? They will never show a black woman, that is of unmixed ancestry, or west African that is beautiful. Often times you will see the pics of meagan good, gabrielle union, and other black American women used, when in fact, black Americans tend to have 20%+ mixed ancestry on average. So why is it you rarely see the pro-blacks of this section use alek wek as an example? Is it really a subconscious, subliminal message? That you are unintentionally admitting women with black features and jet-black skin cannot be attractive?