If regular exercise were a drug, people would stampede to buy it at any price. It is more effective for prevention and treatment of near all common chronic conditions - and for healthy people too - than any presently available medical technology. The only thing to match it (and even do somewhat better) is the practice of calorie restriction. To be clear, you can't exercise your way out of aging to death on a broadly similar schedule to your peers - but exercise does correlate with a longer life expectancy, and given that we're in a race between aging and the development of rejuvenation biotechnologies to reverse aging, it would be foolish not to take every proven advantage along the way.
If there were a drug that treated and prevented the chronic diseases that afflict Americans and we didn't give it to everyone, we'd be withholding a magic pill. If this drug was free, in a country that spends more than $350 billion annually on prescription drugs, where the average 80-year-old takes eight medications, we'd be foolish not to encourage this cheaper and safer alternative as first-line treatment. If every doctor in every country around the world didn't prescribe this drug for every patient, it might almost be considered medical malpractice.
We have that drug today, and it's safe, free, and readily available.
Exercise has benefits for every body system; it is effective both as a treatment and for prevention of disease. It can improve memory and concentration, lessen sleep disorders, aid heart disease by lowering cholesterol and reducing blood pressure, help sexual problems such as erectile dysfunction, and raise low libido. Exercise does it all. Even with cancer, particularly colon and recurrent breast cancer, the data show clearly that exercise is a deterrent. Newer studies on a glycoprotein called Interleukin 6 suggests that general body inflammation, a factor in almost every chronic disease, is reduced by regular exercise.