I think it unfair to label guys that don’t want to get married as fearful of commitment.
I was married 3 times, 35 of the last 38 years, and I’ll never get married again. I’m not afraid of grizzly bears either, but if I run across one in the wild I’ll give them lots of room and stay down wind. I’ve been in a monogamous relationship for the past few months, and maybe it will last for years – we don’t know. But there’s a better chance it will if we at least avoid marriage.
Lots of people change when they get married. It’s like they’re on their best behavior until they get you to commit. Then after months or years, you’re committed to someone that isn’t the same person you committed to. Not getting married keeps things more honest in my experience.