Mostly for the safety of the vet!? I am a vet and animals feel pain same as people. I assume people who make these statements are just ignorant and don't care to educate themselves on the subject. Better to not feel guilt upon purposely inflicting pain on God's creatures. Livestock are often castrated at a young age with little or no pain medication due to economics, that is not to say it doesn't hurt. Caponizing is a very invasive procedure, as invasive as doing a hysterectomy on a cat, dog or woman. The procedure should be performed as a sterile procedure with anesthesia by a knowledgable person.