One reason to bike for transportation: living longer/better life
With the rise of automobility as the primary means of transportation in the United States, as well as a shift from jobs involving a great deal of labor to office-based (sitting) employment, people exercise a lot less.
An important reason for my choice of biking as transportation has to do with the health impacts. My father died in his early 50s, so did his brother. Their father died in his late 40s.
Another reason I chose to bike is that I am not so organized and "hard core" so that I would join a gym and work out regularly.
Health-wise it helps that my first job in DC was for a nutrition health advocacy group, so I learned a lot about nutrition--even though it still took many years for me to begin to cook for myself.
The Washington Post ran a couple stories over the past few days on the significant rise in the rate of premature deaths on the part of white women, especially in rural areas. The early deaths tend to be result from what are referred to as "lifestyle choices" -- drinking, smoking, using drugs -- although the article attributes this in large part to anomie, malaise, significant changes in rural economies, etc.
A couple paragraphs from the second story ("Why death rates for white women in rural America are spiking") confirm the value of my biking (and not using drugs, drink only a bit, and try to eat healthfully):
Other trends may be contributing to the die-off, including obesity. Americans are the heaviest people in the world outside a few Pacific island nations; more than a third of adults in the United States are considered obese. The average American woman today weighs as much as an American man did in the early 1960s.Even though I have now outlived my father, and I could do more (weights, eat even less meat), it could merely be happenstance.
Obesity causes its own kind of liver disease and can be lethal in combination with other conditions, such as diabetes, heart attacks and strokes.
(Note that biking doesn't help me lose weight. But I maintain my weight through this form of regular exercise that simultaneously gets me to and from places.)