You mean the one thing that is responsible for all 7 billion people on the planet? Something that [mostly] everyone on this planet will experience at least once in their lifetime? Do we really need to hide it that much?
Apparently. There's no other reason for it. Just like people flipping out about breastfeeding in public. You can't even see the nip, unless it's a slip! It's perfectly natural. But because people can't NOT make everything sexual, it's disgusting and degrading. It's natural, ignore it and don't make such a big deal out of it, gawd.
Then again, I can understand trying to slow roll kids being exposed to such things. Considering 12 year old kids are having babies and such, it's probably too late though!