If you run every basic calculation through a calculator, you'll make every task take 3x time it requires today, in best case.
I have seen people eyeball measurements and taking notes, and bringing in perfectly manufactured goods (blinds, cupboards, etc.) in return. Esp, in construction, nothing is precise, so being able to eyeball correctly after a quick measurement with a tape and doing some basic math on the numbers, not only accelerates tasks, but is a crucial pillar of being able to work on construction sites, and be productive.
I just left a comment on a different thread about detached from reality a lot of tech workers are, and then here I find a guy being like "but rugged calculators are a thing, why do you need to do math in your head?"
Tell me you have never built a thing[1] in your entire life that was more complex than an IKEA bookshelf without telling me that challenge: I do hobby projects all the time and I couldn't even tell you how many mental-math problems I do per hour while doing so. It's a LOT. Depending what I'm making I might well spend more time doing math in my head and on paper than I do actually putting tools to materials to build the thing.
[1]: by this I mean actually building. With your hands.
Hell even installing shelves in my closet had me doing trigonometry on a scrap of printer paper to figure out how close I could space together the shelves and still be able to get the boards through the door frame.
Calculation is one of the core skills of human cognition and is correspondingly foundational for just about all of human enterprise. Not doing it means limiting your ability to participate in said enterprise.
I never said you don't need to do math in your head. I said that the argument "calculators are fragile, so you have to do math in your head" doesn't hold water. You're arguing something different, which I tend to agree with.
I have seen people eyeball measurements and taking notes, and bringing in perfectly manufactured goods (blinds, cupboards, etc.) in return. Esp, in construction, nothing is precise, so being able to eyeball correctly after a quick measurement with a tape and doing some basic math on the numbers, not only accelerates tasks, but is a crucial pillar of being able to work on construction sites, and be productive.