Alright, get off your high horse. Just because you "excercise" doesn't make you better. There are plenty who don't need to because they work with their hands and plenty more because they have active hobbies. And while it's a popular notion that constant activity makes you healthier, it's just common sense that the body is a machine and the more you stress a machine, the likelier it is to break. See athletes for common ailments.
Except a biological system gets stronger if you stress it in a progressive manner. While athletes constantly pushing themselves certainly do get injured, doing nothing seems to cause far more harm long term. Everything from heart health to bone density is usually better in an athlete.
Almost everyone in my family is obese with a host of maladies. I've been running 23 years and am incredibly healthy despite the occasional hamstring pull or achilles tendonitis.
This is a good point, and it's a good idea to pick a form of exercise that has less impact, (at an extreme end, I'm sure that the skiiers who do mogul racing are in great shape, but their knees probably don't work so well after a few years) but keep in mind that the body repairs itself. As long as you aren't repeatedly destroying your joints, you're going to get a lot of benefits from exercise.
In many cases, athletes are less likely to get injured than the sedentary population because of increased strength and flexibility.
And I bet those aren't the people about whom the parent was talking. It's not as if the benefits of exercise are unknown or controversial. Everyone knows that they are better off being active. Therefore, people who do not spend time being active are at the very least making a choice, if they legitimately have a more effective way of benefitting themselves, at most making excuses, if they do not have such a way.
The body is a biological organism, not a machine. Biological organisms that suffer disuse experience atrophy, wasting, and decay. Chronic controlled dosages of physical stress produce salutary effects in the human organism. Muscles grow and strengthen, bones increase in density, range of motion is preserved and increased, cardiovascular capacity increases, and even cognitive function is enhanced by exercise. You could not have summoned a worse analogy for the human body if it had been your intent.