In my experience, people who compete regularly improve more rapidly than those who don't. If you are in an area where you don't have a multitude of tournaments to choose from, gambling may be the only way to compete regularly. Most of the players I know who have been playing for 20-30 years and have plateaued at the C or B range are the type who, for whatever reason, hardly ever compete.
Maybe it has something to do with how competitive a person is? I'm not very competitive myself. I don't play well for funsies, because my goal is never to beat someone. If I'm competing, my goal is to make as few mistakes as possible and see what happens. I have seen lots of people who can't stand to lose, though, and they seem to just focus on "damn I want to beat this guy", and they often end up playing under their true speed. Probably some of those people refrain from competing because they are so afraid of getting beat. They might avoid a little humility, but in the end I think they are suffering a much bigger cost in their advancement as a player.
Aaron
Maybe it has something to do with how competitive a person is? I'm not very competitive myself. I don't play well for funsies, because my goal is never to beat someone. If I'm competing, my goal is to make as few mistakes as possible and see what happens. I have seen lots of people who can't stand to lose, though, and they seem to just focus on "damn I want to beat this guy", and they often end up playing under their true speed. Probably some of those people refrain from competing because they are so afraid of getting beat. They might avoid a little humility, but in the end I think they are suffering a much bigger cost in their advancement as a player.
Aaron