as other have said, reason numero uno is "fun".
i don't own an automobile (by choice) so my bikes are my main mode of transportation - commuting, running errands, visiting family/friends, exploring, etc.; they carry me all over chicagoland. cycling is more than just mere fun; it's a spiritual experience for me. i find the magical synergy between man and machine represented by the bicycle to be transcendent. my body feels astoundingly fantastic after a good ride, but the awesome part is that my mind feels even better.
i get a similar zen-like feeling from kayaking as well.
Last edited by Steely Dan; 08-26-10 at 03:53 PM.