Eh there's a difference between a job that can be accomplished with on the job training and the right soft skills, vs a job that requires a degree or apprenticeship or something similar
Ultimately it depends on liability and how replaceable you are if your employment terminates. Not that that mindset is a good thing, it's still exploitation, but that's the thought behind it.
Masonry and farming can be complex tasks requiring substantial training too.
Same with a bartender. In many places you need to get specific training for serving, so you don't over serve, and know when to cut people off. On top of that, there's a long list of drinks and cocktails that you're expected to be able to put together at a moment's notice. It's far from unskilled IMO.
I mean, if you're just pouring beer from a tap to a glass and not much more, maybe? As soon as you need to mix, it's much more involved.
Don't get me started on bricklayers/stone masons; definitely not unskilled.
Most of these jobs are benefited by skills. Even a cook or dishwasher, having prior cooking experience or training, even if you're working at a fast food place, having food safety and good kitchen habits and etiquette, so you don't walk into someone standing at the fryer or something - it's still a learned skill.
IMO, the "unskilled labor" title is not accurate, it implies anyone of any skill level (including zero skills), can do the job, which is completely incorrect. There's no way. What it should be, and what it means in my mind is that this is labor with no specific prior knowledge required, which is any task you can learn on the go. If you can show up, never having done the job before, and learn as you go and be not garbage at doing it before the end of the day, then it's a job that doesn't require specialized skills or training to get. It should be marketed in job ads, more like "on the job training" and that the job does not require any college/university, or prior experience.
Anything referred to as "unskilled" is always going to be wrong in my mind.