Bad health is terrible for your quality of life, but also for your wallet. This is not a part of any cost of car ownership calculator.
Have you heard the phrase "sitting is the new smoking"? It might not be exactly true, but there's very much something to it. And what do you do while commuting in a car? You sit, you deteriorate your health.
What do you do when you bike? You move, you elevate your heart rate, you build muscles, you're engaged in your surroundings.