I can think of several, one male who has now cut and split nearly 50 cord of wood this summer/fall to sell this winter. He's on his tractor, pulling logs out of the woods daily, he carries 50 pound bags of grain over his shoulder. Drawing disability due to a permanent back injury that prevents him from being able to do construction, his previous career ?. He's an intelligent guy, he could easily get a job in sales, behind a desk, teaching school, ......... where he didn't have to stress his back like he is doing cutting wood. He's set to make about $5-7k on the wood he's cut, that he will not be turning in on his taxes.
I know another gal,in her early 40's who is about 350 pounds, and needs knee surgery, she cannot walk w/o pain. She had a desk job, walked to and from her car into the desk, less than 100 yards total/day. Permanent disability and an endless supply of narcotics vs. doing gastric bypass followed by knee surgery on a person who is mentally fit, and otherwise physically fine, no other comorbid conditions other than obesity at the moment (wait another 10 years though, and she'll be diabetic, and have a heart condition). Instead of paying for the surgery, so she can be a tax payer, and continue her job answering the phone, she's on disability. I suspect they will re-evaluate her in a couple of years, but by then she'll be heavier, and dependent on narcotics, and no one will want to do surgery on her.
Both of these are examples of folks who I know intimately. I have complained to SS, but it's resulted in nothing that I am aware of.