Why does it hurt when water, soap, etc. touch a cut or scrape?

Because it's raw. is cut the, shall i say, sturdy, skin and the layer of skin under the sterdy skin was not ready, so it's raw flesh. And raw skin is extremely sensitive and when chemicals or something moves, rubs against it, the nerves respond in a painful way. That's my hypothesis. I'm not a dermatologist. But you can ask one.