Why always boobs, butts, or balls?

Why couldn't my mammalian brain first assume something interesting like a resemblance to the bottom of a protein synthesis chain, an allegorical reference to the Mickey Mouse copyright expiration, or even something as tame as siamese pinot grigio?

I see an image, my brain clicks the first naughty pop-up like a boomer browsing on an unofficial youtube downloader site.

TLDR; Nice grapes!