You're overlooking the kind of life-long medical expenses that can come from even a short career in pro sports, though. As soon as that teenage springiness and resilience is gone even minor injuries can add up fast.
Any sustained outdoor work like landscaping, roofing, and plumbing is brutal on the body in the long-term. Even the salty old kitchen workers I've met eventually start falling to bits.
Star athletes are also inculcated with a conscientiousness around health and fitness that desk jockeys and eggheads don't have the benefits of.
You're right, this is pretty atypical for runners in general, but unfortunately not for my high school team. Last I'd heard about 50% had been through at least one round of surgery in college, though my sister's definitely one of the worst for wear.