For me it almost happened by accident. I'd been a motorcyclist in my misspent youth, and a few years ago my wife decided to get a scooter for short runs around town. (We were a one car family, and at the time I needed the car to get to work.) We grabbed her an agility 50. However, she had an unfortunate first ride, dumping it within seconds, ending up under it and injuring her knee and never got back on it. When I switched jobs I started using the scoot to get to the office because with that I didn't have to pay downtown parking rates
Fast forward a few years and the garage then contained 2 agility scoots - the 50, now completely derestricted, and a 125 I'd acquired as a non-runner and repaired. Then they shifted my office half way across the metro area and I needed something seriously highway capable. At that point it was a matter of making the "maxi-scoot or motorcycle" decision. Having thoroughly retrained myself to scooter controls by this time, the 50 got sold to a friend and it's space in the garage is now occupied by an xciting 500.
I don't see myself ever going back to a motorcycle at this point, although the new Indians might have a chance of tempting me back from the dark side