We make walking, riding public transit, and bicycling expensive and driving cheap. Walkable, bicycle friendly, transit oriented neighborhood have been restricted there aren't enough to meet demand driving the price up. Walkable neighborhoods tend to be more expensive than car dependent neighborhoods this should encourage builders to want to build in this kind of place because they would actually get better prices for their buildings. We don't have more because we actually restrict this kind of denser neighborhood with parking minimums, height restrictions and it does take quite a bit of planning to build a bike route. In places where there are bike routes they do get used extensively.
The reason this concerns me is that we make it so hard, dangerous, and expensive to get any exercise which will of course lead to more diseases. We are not doing the simple things on the level of society to be healthy and then trying to rely on high tech medical research which I work on. The high tech medicine should be the last resort when things go wrong and things will go wrong often enough that we don't need to add to health problems intentionally and I think we are by subsidizing driving cars so much and making it hard and even dangerous to walk, bike, or go outside without a car around us.