Riding is freedom, being part of nature, part of the road, the sights, the smells (especially in farm country or behind a cattle truck

) the unknown destination, the camaraderie that one feels with like minded folks. It's just something you cannot experience in a cage, even a convertible does not give you the feeling that riding your trusty steed does.
In a car you see the movie of the landscape passes by... On a motorcycle you are in the movie!
I've never been happier than being by myself on my bike on a road that stretched to the horizon. Feel the sun, the wind and the rain, get in touch with your surroundings. To clear my head, I need a ride on my Valk.
Something like that..
These two explanations closely parallel what I tell my friends about traveling on a motorcycle. On a bike, in the wind, you are part of the world around you with smells, sounds and feelings. Traveling in a cage is like sitting on the couch and watching the world on TV.
It's not entirely why I ride but it is part of the experience.