I have been taught that you ride bitless (for both rider and horse) until you don't need a bridle at all, then you ride bridleless. Once bridleless is good you then ride with a bit to help shape, not control, the horse...
I believe you were taught wrong. Of course bits were and are used for control. That does NOT mean they are used to punish a horse or to inflict pain, but they are important means of control.
I spent much of my adult life on a flightline. F-4s, F-111s & even a tour in the EA-6B at Whidbey Island. When you walked out on a flightline, there were jets running. Even if you were the first launch of the day, there would be someone running a powercart or doing an engine check. There is a reason we wore earplugs, and there is a reason my hearing is marginal after years doing that. You often had to shout at someone to be heard. You sometimes had to touch them so they would know you wanted them and could focus on you.
Of course, in a library that isn't true. You don't start shouting in a library, and you shouldn't need to grab someone to get them to pay attention to you.
Horses are like that. A relaxed horse, walking in an arena, is in the library. When Mia is in a library, her listening is acute. She can 'hear' my legs, and she can hear it bitless when I take some slack out of the reins. It is easy to hear, in a library.
But horses don't always walk in an arena, and some horses are more excitable than others. And when a horse gets excited - fear, joy, speed, another horse, etc - they leave the library and go to the flightline. Horses are emotional creatures, and their emotions cause background noise. As their emotions get stronger, their ability to 'hear' becomes less.
A horse who sees a coyote just ahead and is afraid, or a horse focused on working cattle, or Mia when she gets to run next to another horse...they're on a flightline surrounded by jet engines. You need some way to cut thru their emotional noise and get them back in touch with YOU. And that is why we have bits.
A bit isn't there to cause pain. It isn't a torture device. It doesn't punish a horse. It is a communication device. The reins are like telegraph wires, sending signals to one of the horse's most sensitive receptors: the mouth.
A bit is an amplifier. It helps get past the emotional noise and help a horse hear his rider. Used at the wrong time, in a library, it is a painful blast of noise. Used on the flightline, it is a critical tool allowing communication. During the in-between places, it allows more subtle communication - talking instead of just waiving arms or pointing.
A harsh bit isn't cruel. It is a strong amplifier. Maybe even the equivalent of when the crew chief for a jet puts on headphones and plugs into the aircraft intercom, so he can hear the pilot speaking. There are no cruel bits, only bits that are stronger than needed or used to shout when a whisper would do.
I rode bitless for 3 years because I bought in to the YouTube Gurus - the videos of how bits are cruel, or people like Rick Gore
"Answer:Metal bits in the mouth = Less Horsemanship, more pain, and a lack of partnership between horse and rider...Pain rarely makes a horse feel safe! Bits = Pain, especially when both rider and horse get scared and or nervous."
I was wrong, and so are the Internet Gurus who preach bitless without understanding why bits are used. That doesn't make bitless wrong. For a lot of horses and a lot of riders, bitless is all it takes. My Appy/Arabian gelding is a much calmer horse than Mia. He prefers a bit, but he is quite safe to ride bitless. Some horses NEVER leave the library. Others, like Mia, spend very little time there - so pick the tool that matches your horse and your riding.
Internet picture that brings back memories: