In the United States a lot of our health and wealth is tied together with our cultural emphasis on driving a car to get anywhere (even if its a 5 minute walk!). People would rather sit in gridlock traffic for hours just to uphold the American ideal of the "freedom" of owning a car.
In reality, if they hopped on a bike, they could fly past all the traffic and be home much faster and with a great workout!
Unfortunately, a lot of cities either have no infrastructure for bikes or the infrastructure that is present is not safe.
Instead of paying $4.3 trillion a year on healthcare, maybe we could use some of that to build bike paths and teach people how to bike to work safely? Crazy idea, I know