That's honestly a hard question to answer in the general sense because every man seems to join for different personal reasons. Some join to network, others for secrets, others for philanthropy or brotherhood. Some are just retired men looking for something to occupy their time.
Likewise what would be considered a benefit will vary from man to man. But I think most people would consider the brotherhood and community to be the greatest benefits. It's pretty amazing to know that if you ever found yourself in a tight spot anywhere in the world where Masons live you have a group ready and willing to help you out.
But to answer your question about my reasons, I joined because I had always wanted brothers and male role models since I was the only guy in my family. I found that my college Fraternity left something to be desired in that regard.
As it turned out, a couple of my fraternity brothers joined the Masons and I liked what I had heard. They were mostly men ranging from young professionals to retirees. When I met the Masons they were all very kind and respectful. They invited me to a philanthropy they were doing, which I really enjoyed. I really just felt that I had found a group of men I could learn from and grow with, who had a good sense of decency and humanity about them, and who really wanted to become generally better versions of themselves. It just resonated with me. So I put in an application and never looked back. It's honestly one of the best decisions I've ever made, but I know it's not for everyone.
I hope this answers your question. Thanks for asking!