Bits are like pebbles in your shoe. Always uncomfortable. This is regardless of the rider’s level of softness, or even if the reins are resting on the horse’s neck, untouched by human hands. (See: Clemence.pdf)
Depending on where they poke you, the discomfort can range from somewhat tolerable to extremely painful.
Imagine, for a moment, you work as a delivery person, on foot, and that you have a smooth, round pebble in your shoe. The size doesn’t matter because it will drive you nuts whether it is big or small. Now, imagine that your shoes can not be taken off until you finish your shift. No matter what.
So, you walk funny and shift your foot in your shoe the best you can to find a more tolerable spot for the pebble. You are distracted by it, and, even when your boss is talking to you and giving you orders, your attention is divided. The boss notices your foot bending this way and that way, and decides this is not a good look, so, he straps a leather band around your shoe to stop you from shifting your foot around and moving the pebble all over. The pebble is now in the spot you most dislike, the spot you were trying to avoid. There is nothing you can do for relief. Worse, still, your boss insists you stop limping, or you’ll get no pay.
Nosebands are positioned to strap the bit into one place, where it can not be escaped, regardless of the level of discomfort. Their use implies the horses are uncomfortable enough to try to move the bit around to get relief. The answer, apparently, is to force them to deal with it for the sake of meeting competition rules which, oddly enough, state that acceptance of the bit is a requirement. Clearly, a horse who has to have the bit strapped to his mouth is not a horse who accepts the bit. Yet, nosebands are allowed under the same set of competition rules. How does that make any sense?
https://www.naturalhorseworld.com/wp-content/uploads/2020/02/tobitornottobitJClemence.pdf