Korean history was a bit different. If you look at the Koryo and Choson Dynasty for example, you were born into your class. If you father was a military officer, then you were pretty much destined to do the same. If you were born into a scholar family, then being a teacher was in your destiny. After King Sejong's reign class mobility became possible. Example there was a slave who had extrodinary intelligence so much so that King Sejong gave him a position in developing weapons for his kingdom. But i digress..Mostly upper class would learn swordsmanship and archery. Very few if any would learn H2H. More lower level military would learn those tactics.
If you were not in a military family then your parents would most likely higher a tutor to teach you these arts. Depending on your reputation or status you could make a nice living. Now let's jump forward to after the Japanese occupation. You had a mixture of Koreans who taught both as a living and as a side job. Eventually many of them taught full time. Some went on to make a great living at it, some fell back into their chosen profession before martial arts.
The overall point is that it is a myth that all past great teachers taught for free. It just depended on their specific situation. Just like all the really great teachers taught only in secret or only to selected few students.
Sorry to hear about your poor experience with Taekwondo. While I was still taking lessons, I sort of had the same experience, though I was at least lucky enough to train with the instructor that had competed in both TKD and kickboxing. He emphasized the practical techniques of TKD while still teaching us the signature forms. He also allowed us to use the very few sweeps from the one-steps in our sparring sessions against each other. With that said, not all TKD dojangs are bad. However it is good to know that you've found martial arts that you feel are more fulfilling to you, and that is what really matters.