You are sounding like you have never worked in a job like this. I have worked for a carpenter and an automechanic. Ever seen someone unable to even get the heat shrink wrap off a pneumatic tool and replace the lines? I saw someone unable to do it and end up gashing their hand as they were trying to cut it off. Ever work under a hot engine bay for 8 hours? Holding your hands above your head the entire time, and developing pain in your neck? Ever used an angle grinder? Should I trust you with one? Ever lifted 300lb pieces of granite, cut them to size and polish them? That's hard work. Do you think you can do it?
Besides, by focusing 100% on this physical aspect you're nearly just attack a straw man argument and ignoring the substance of everything else. Not every person is exactly the same and it doesn't matter. Get over it.
Seen someone screw up because they weren't trained: yup.
Work under a hot engine bay for 8 hours: no, but I've worked outdoors carrying construction material during heat waves, and I've worked indoors in cold data centers.
Holding my hands over my head until pain develops: yup. I don't recommend it to anyone.
Used an angle grinder: no. I have used lots of other power tools. Should you trust me with one? Not until I'm trained on it.
Lifted 300lb pieces of granite: no. We have these things called wheels, you might have heard of them? Using wheels and levers and ropes and pulleys, I have moved much heavier things. I recommend using appropriate tools. Hoists? Cranes? Block-and-tackle?
Besides, by focusing 100% on this physical aspect you're nearly just attack a straw man argument and ignoring the substance of everything else. Not every person is exactly the same and it doesn't matter. Get over it.