While its basic math you would be surprised at how many people have forgotten about PEMDAS. I would argue that the additive way comes more naturally to people. For people wanting to more complex equations scientific one does follow PEMDAS.
These days for actual physical calculators, and on phone, I've transitioned to RPN which neatly transcends such petty ambiguity problems.
Once the computations get complex enough that you have to write down the formulas, then it makes a lot of sense to treat the computations as algebraic expressions, meaning PEMDAS.