Very simple. Because those jobs were once available in mass without an extremely expensive risk of college debt, often unionized and provided good stable salaries that raised many millions of healthy families and provided pensions that have allowed for healthy retirement.
I live in a former socialist country, many kids saw their profession just like this.. elementary school (8 years, ~7->15yo), technical high school, and then work at a local factory for 40 years. And they did exactly that. Only the best few in class went to gimnasiums (general highschools, thought of like prep for college), and then to colleges to become "more". The wide middle of the bell curve was for high school graduates working in factories. And not just factories, some wanted to be automechanics, some electricians, etc.
Now everyone wants to go to college, many to study something where there are literally no real jobs (with added benefit) available (ancient greek, comparative literature, sociology, etc.), and then end up in the public sector, where it doesn't matter if you studied electrical engineering or latin language, all college diplomas are worth the same.
I mean sure, everybody wants to be a superhero, etc. (or pewdiepie-sized influencer for the more younger generations), but once you're 14yo, ending elementary school, you have to choose your next level of education (general gymnasium, one of the technical highschools, economics, construction, cosmetics, etc.), and back then a lot more people chose their actual future careers at that moment than now, where parents push them to gymnasiums, colleges, where some fail (and some somehow succeed), and you then have baristas and warehouse workers with masters degrees and not enough electricians, construction yard workers, factory workers, etc. (electricians etc. are especially bad, because you actually need a high school diploma (or similarly hard alternatives) to do the job).
