Working on something at your house is very different from doing it day in and day out, year after year. I have worked many manual labor jobs over the years and after just a few years started having constant pain in my knees, feet, and lower back. My father has been in a trade his entire life and in his late 50s, he was already having many physical issues from it. Not everyone can just take on an apprentice - especially since this article is stating that nobody wants to do these jobs.