Yeah, I think not sounding gross or dangerous is part of it - combined with the skill level. Personally, my in-laws encouraged my nephew not to go to college, but instead to become a welder - or an electrician as a backup plan.

He did neither and now works for the city cleaning sewers. It's a needed job and pays ok, but no one ever says "you don't need to go to college, you can clean a sewer." It's always "you can be a welder."