What's the use of joining a fraternity/sority?

They usually own townhouses.

Now I understand why someone said it was for well-to-do (at least) parents!

Not necessarily for the well-to-do. You have to live somewhere. My fraternity in college provided housing and board. It was a group of guys who are still life long friends. It was all about academics, sports, a social network and just plain friendship. By the time I got there hell week had been replaced with help week. It was for many of us, a home away from home.