For the first years of school, it is actually very beneficial to pretend that calculators don't exist.

Students must be accustomed to do simple arithmetic without the help of a calculator, or else their mathematical abilities will be negatively impacted. Same for learning multiplication tables, recognizing the associations between the numbers is important.

Only when they begin to calculate things which exceed the number of mental tokens that they can handle, then they can start using a calculator with no ill effects.