These threads are scattered around on Bike Forums ... however ...

I started riding because my parents cycled and they got me into it.
I continued cycling because I enjoyed cycling and I enjoyed the freedom it offered.

My cycling dropped off a bit and I started to focus on other aspects of fitness.

I resumed cycling to train for an event and because it was the cardio component of bodybuilding.
I continued cycling because I enjoyed it ... it was a great way to see the world. And it keeps me in shape.