During the Arab Oil Embargo of 1973, I vowed never to sit in line in an automobile at a gas station. So I parked my old Dodge pickup and started cycling everywhere, including weekend vacations to neighboring Midwest towns, visiting friends in college, etc. In 1975, I took off on a 1000-mile trip around Lake Michigan from my home in Chicago. That's what hooked me on longer self-supported trips and confirmed the lifestyle for me.
I couldn't figure out why I seemed to be the only one doing that. Fun, cheap, healthy...why was this a secret? Then in 1976 I heard about the BikeCentennial and learned others were doing it. A few years later I met the cycling woman I'm still married to and still cycling with.
So I guess it mainly came down to an economic trigger. And it was a good decision. My wife and I attribute our early retirement, and good health during it, directly to a cycling lifestyle. All those years without driving, and being able to stay away from the "health care" system, rapidly compounded our savings.