Barring accidents, injury, or bad luck (e.g. a car crash or something), you can absolutely save enough to retire as a plumber before your body starts to break down. Especially if you assume SS will still be around for a new plumber's retirement, which may or may not be the case. Even without, it's doable. I know two plumbers socially and both are in their late 40's. One owns a plumbing business so mainly does office/marketing tasks but one is just a standard plumber and does plenty well for himself and his family.
Which brings up another issue: manual jobs involve non-trivial amounts of physical risk. Not only does getting injured negativly affect your life you will always do better working than on disability. And I agree that it's possible for some people to own a business or or do office work, but not everyone who is a plumber today will be able to do that. There are fewer owners than workers.
I don't think we should discourage trades, but we can't sugar coat them either. I used to work as a mechanic and never met one that was 65 (the SS retirement age). The safety nets in place are optimized for people who work office jobs, not manual jobs.
This ^^, you can do well as a plumber and retire after 2 or 3 decades of working if you play your cards right, leaving you with a fairly functional body and freedom from working 1 to 2 decades ahead of most people in the US.
