Why is cycling addictive?

I'm curious to know, why exactly is cycling so addictive for so many people? Is it the thrill of the wind rushing past your face as you pedal down the open road? The endorphin rush that comes from exercise? The sense of accomplishment after reaching a new milestone or summit? Or could it be something more subtle, like the feeling of being at one with nature and the world around you? I'd love to hear your thoughts on what makes cycling such a compelling and addictive hobby for so many.