What proof do you have? I think you're wrong. They do feel pain but know what they are doing is a net positive. Sort of how civil war injuries resulted in amputations. A lot of amputees back then definitely felt pain.

Until the 80s, many medical professionals believed infants could not feel pain due to an underdeveloped nervous system and performed major invasive surgeries in babies without anesthesia. Doctors sometimes used paralytic agents to keep the infant completely still instead of pain relievers. It was horrifying when I found out about that.