" I don't like these posing penises"  But you can make little costumes for them and stage skits.

"Is it some sort of ethnic thing?" I ain't gonna go there with regard to any of the Japanese implementations - notorious old joke about Occidental myths and Asian female genitalia. Arduino, viceroy of vaginas, lord of labia, count of - well that guy is Italian I believe and AFAIK there is nothing especially odd about Italian lady bits. In the interest of science however I will research this further.

 Years ago, Zygote (or perhaps Daz by then) supposedly stated that in their opinion there was no artistic need for anatomically correct female figures. I assume that meant that any pose which would reveal the omission was not artistic, though as Momodot points out, for most females that would leave you with an extremely limited range of poses for nudes. It seemed maybe just a wee bit sexist to me but others suggested a lack of access to, or familiarity with the requisite source material. 

Whatever,  the introduction of the gen_crease morph with V3 was a welcome change and probably adequate for non-erotic/non-medical images. Miki, Maya Doll and Have's Eroko have decent built in pudding. All of the bolt on accessories and after market pudding cups suffer from the dilemma of texturing. As LMK observes, there is enough natural variation in host/toast skin tone to give you some leeway - though perhaps more so for Caucasians. Pudding doesn't seem to mix and match so well to my eye especially when the texture has to blend into the rest of the pelvis.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken