That is not so bad to depress some of those wages, my plumber is making $2k/Day. I don't know too many people making that kind of money even in tech, let alone other disciplines!
Lol tell that to my dad who is still painting houses at 63. Or his competition who is still painting at 70. that is preposterous. In fact most laborors I know are well above 45. Yeah it takes a toll on your health but most of the health issues I see in labor intensive jobs is because of alcoholism. Its good for your body by and large to get up every day and do physical work. Yes your back will hurt, and your feet and your joints. But you'll be in good health.
Think construction... welders... carpenters... plumbers... guys who smash appendages and crawl around in mud.
I know quite a few old ones and I know many many more who struggle with pain every day as they are my age and talk to me about it. ( IT being my 3rd career after welding and meatcutting ) I have many friends who are dropping out of the workforce and finding alternative jobs because they cant do the work.
Painting is hard work but its one of the less body impacting you can do. There are a few roles like that and yes, being active is a good thing.
There's more to running a plumbing company that just the person who shows up at the job site. Plus, plumbing isn't a one-person job. Every plumber has helper/apprentices, etc.
How is that different from when I take on contract tech work and farm out some of the work. everyone has these types of problems when they are sole proprietors.
I believe you're confusing top-line revenues and profits available for the tradesman. As it stands, you're asserting that your plumber makes approximately 14x the average plumber in America, and 10x the average plumber in San Francisco. This is unlikely to be correct.
In a similar vein, Apple takes in over $2,000,000 of revenue per employee, but Genius Bar employees are not taking that amount home. I mention this solely because it uses the same reasoning evident in your initial claims.