It's unnecessary but a lot of pain medication is "unnecessary." We use it to reduce pain because we don't like to feel pain. This seems self evidently common sense to me. In New Zealand my colonoscopies were carried out with ketamine, which is incredibly safe under medical supervision. Unless there are contraindicated medical conditions, I see no reason not to use something like ketamine or a light dose of oxygenated nitrous oxide.
In Poland they give you option for sedation, but advise against it because sedation disables the feedback from patient and that slightly increases the risk of complications. When they do the procedure they ask how you feel and when it gets too uncomfortable they change the angle etc.
I've had like a dozen of colonoscopies (have to be checked every year cause of risk factors), and they were never really painful.
Nitrous oxide is a fairly strong anagelsic (pain medication) but a very weak sedative. That's exactly why it's often used for minor routine procedures where keeping the patient awake and reasonably alert is more valuable than keeping the patient fully sedated.
