Earlier quoted context omitted.
In part because you have to jave enough sr people able to mentor. There's not a great industry framework. As a plumber, you pay your apprentice usually 60% sr/journyman salary with a 5% increase every 6 months to match the value of the skill up. There are also industry standard, industry funded classroom settings, that teach things like building codes and industry standards and some adjacent trade craft. Instead you…
When you say "industry funded", who specifically are you referring to? Tool / parts / consumables manufacturers? The individual plumbing firms?
But industry standard groups, unions, people who have a vested interest in having a supply of quality labor so they can do business. Some of the classes are sponsored (especially in smaller places where there's not enough support) and in return, they get to train you on a specific product or just hang a banner and give you a 10% tools coupon.