Kinda like we have sensors all over the place, but the info a lot of them deliver (pain) is pretty vague. And because of how it gets aggregated and delivered to the brain, sometimes you have funny glitches like how I can scratch the inside of my left ear and it makes me cough.
This is what hit the NSA.
I guess evolution beats at the pace of signal to noise ratio
https://www.icd10data.com/ICD10CM/Codes/K00-K95
Evolution really looked at this big long list of gastrointestinal diseases we as humans can suffer from, and thought that traumatizing amounts of random nausea, constipation, diarrhea, and tummy hurt would be enough for us to figure out when we're supposed to be eating more nuts and less berries, or whatever the hell. I hate it.