Because better movement is a high payoff improvement. Everyone will have a better life if they can move better. Life imposes physical demands and life is just better if you can accomplish those demands with energy, ease and grace. If the physical demands of life exceed your movement fluency, then you will experience chronic stress that will cause pain, reduced energy, and overall loss of enjoyment of life. You won't perform your job as well. You won't be as nice to your family. You won't have as much fun hiking or traveling. You'll get old sooner. These are simple facts and most people seem to ignore them. I notice that most people spend more time and effort and money taking care of their cars then their bodies. Some people even build little houses for their cars called garages so that the car doesn't have to get rained on. Why not turn the garage into a home gym? Anyway, the main point here is that everyone's life has a physical dimension, not just athletes. Even if you just sit in a chair all day or raise kids, these are physically demanding tasks and your body needs to be able to withstand that stress. So, to steal a phrase from Eric Cobb, the creator of Z-Health: Life is a sport - train like an athlete.