Because the vast majority of factory work is not backbreaking labor. It typically involves running machines, taking QC measurements, performing maintenance, manning estops, 5s etc. Yes, there are days that suck and they can be exhausting, but most factories don't have days like that very often. Everyone knows the ones that do and it's best to avoid those plants.
So why wouldn't people downvote the person who said the work will destroy your body, or the one who said you can't sit down?
I never said factory work is backbreaking. It can vary greatly by industry, but is generally more active than an software dev job but harder on knees and such. Yes, there are some manufacturing jobs that you just sit at a machine, but many of the machines still need someone to load them, reset them, etc.
