Why do people use the motorized carts at Walmart even though they probably don't need to?

I was at Walmart yesterday and saw a man with his kids. He was in a wheelchair, pushing it with his right hand and pushing the cart with this left, as well as trying to keep his kids in check. I then see a large woman using one of the motorized carts. Her legs seemed to be in working order, unlike the man in the wheelchair who could have benefited from the motorized cart. Why is it that overweight people use those carts? Maybe if they walked it would be better for them. I am overweight myself, and would never consider using one of the motorized carts because I have enough decency to save them for someone who really does need them.