Not sure about Japan but in Poland the variables in problems are either symbolic and you solve it symbolically, or if they are given as values then they are usually chosen just right to not make arithmetic much of a bother (that actually results in a fun 'sanity check' that if you start getting something waaay crazier than 'normal' you double check if you didn't screw something up somewhere along the way or if there is a better way to solve it).

But everyone is taught to only substitute variables for values at the very, very end so calculators are not needed at all. At some point in education there is no point in testing arithmetic skills over and over again, the problems and the methods of finding out solutions to them are what matters

We were allowed to use calculators when I took my school exams in the uk. But our exam questions often asked us to give the answers in surds i.e 3/4*√2 not as a decimal which our calculators couldn’t do then. Our teachers told us there would never be a question where the answer couldn’t be expressed cleanly using either fractions or surds, that we should practice doing the maths and show our workings on the exam paper and that if we were using a calculator we were wasting time doing data entry as the actual addition / division / subtraction would never be hard enough to justify it. We memorised a table of surds for 30º 45º and 60º angles but I’ve forgotten why now. Also they hard reset our calculators as we went into the exam.