Yeah.
Work for a summer as a manual laborer some time. Grueling, backbreaking work, unless you have the "in" (and five years journeyman experience at no to little pay) to be a plumber/electrician/heavy vehicle operator.
Every time I've tried working in laboring I haven't lasted a month, usually less than two weeks (till paycheck). Carrying sheet rock, digging trenches, general haul this go over there. People come out of manual laboring either built like a professional wrestler, with severe muscle-skeletal problems, or both.
No one wants to work those jobs because they're so terrible.