They’re too bulky and swingy for most people doing physical work, while also not being able to hold most things they’d really want to, versus typical work pants that might have like one big extra internal pocket on the thigh and a hammer loop maybe but are mostly gonna be about heavy canvas fabric or denim, double-layer knees or fronts, reinforced stitching and rivets in the right places, stuff like that. Your average cargo pants fall apart when subjected to physical labor because they’re not actually built for it, they mostly use low-quality runs of chino-type fabrics of one kind or another, and those damn pockets just get in the way all the time if you actually put stuff in them (and sometimes even if you don’t—they’re very snag-prone).
I think it’s fair to characterize them as faux-workwear, for the most part. Some folks can get away with them and do wear them because they’re cheap and easy to find, but anyone who really wears their work clothes will usually go for something else. Doing handyman stuff around the house, fine. Framing houses, you’ll be shredding a pair every few weeks, and some you’ll probable rip at the seams the first or second wear.
Not many "work pants" even have cargo pockets,