The same reasons other professionals don't do much besides specialize in their own field of work. If you're dedicated to running, recovery is also very key and takes a lot of time. Anyways I know some entrepreneurs and bosses who only really work a couple of hours a week. And why do other people really care what others do? Are they that insecure and bored that they need to criticize others and follow everyone else's lives? Probably. Just do what YOU want and leave others alone.