They are, it's true. And it's equally true that many of those jobs and skillsets have been marginalized, and quite heavily... especially in the last 20-30 years. It really wasn't that long ago historywise that a degree was something most people couldn't afford. Higher education was mostly for rich families, or those few lucky enough to qualify for some sort of grant or sponsorship. And in that time, yeah, you could be all but guaranteed a job when you graduated because graduates were still rare.
But now? Everyone seems to expect that you follow these steps. A: Graduate High School. B: Go to college. C: Continue your education OR D: Go right into a good-paying job in your field. Failure to do this means that you are... well, generally viewed as something of a failure, or have settled for second best, or are lazy, etc. Doing construction, being a plumber, a welder, all of that carries now the stigma of 'labor'. As though labor was a bad thing, and apprenticeships are only taken by those who don't have the skills or intelligence to do something else. Nevermind the sort of skills and talents it takes to be a good welder. Hell, I worked with an arc welder for only a summer at Subaru-Izusu (sp?) Automotive when I was 19, and it took a surprising amount of knowhow and talent to do well. And that was just an arc-welder at one station in the process.
There's just too much focus now I think on office jobs and the like. Which makes sense in a way, as you're indoors and not doing heavy lifting, not coming home all sorts of dirty and worn out from your work. But you make good money for that work, and it's honest, and I've never seen anything shameful in it. Hell, my brother-in-law to be works in construction, and he works his ass off for the money he makes, which already has him a house with his fiancee. Maybe it's not where everyone wanted him to end up, or thinks he's settling, but he likes the work and makes a good living doing it. How many people wish they could say the same?
Hell, I do.