Most people need a little time to themselves.
The bike commute serves that vital function for me. It combines transportation to work with healthful exercise and energized thinking. The mind works differently when the body is working too, as opposed to just sitting.
When you're driving, you're never alone, even if you're alone in your car. Everyone is in their tin cans, buzzing along nose to tail, often pissed off at each other for miles of forced company. Whatever they think of me on my bike, the encounter doesn't last long. Mostly they ignore me. Except when I have to control the traffic, I get them past me as quickly as possible. That's a lot harder to do when I'm driving the same size vehicle they are, at roughly the same speed.
For the next couple of months I will not have a fraction of the exercise or the justifiable separate but equal use of the public right of way that make life much more endurable in bike season. Even on a back road I could see the unwelcome glare of lights coming up fast behind me. On the major roads I can count on getting embedded in crazy trains of drivers who learn more from watching close tactics in NASCAR races than from the wisdom of following distance when driving in the real world.