Yeah, right now, I'm literally drafting a short story about a man turned into a giant penis, and it's tragicomedy horror. Go figure.
As for op, sorry, not a fan of big boobs so I have to refuse.
lack of originality and pandering to tropes, as well as being paid for chapter/word count leads people to create unoriginal stories that are set for quantity over quality
400 years ago
also, this idea didn't originate from the journey to the west, but buddhism and daoism, where cultivation's point is to level up person's soul and remove them from the cycle of reincarnation- through self-improvement of the character