With the widespread availability of calculators, is it necessary for students to learn arithmetic?

Even with the advancement and widespread availability of calculators, it should still be necessary for students to learn arithmetic. People don't usually carry around calculators and the ones that are on the phone can only do basic and simple calculations, so by knowing how to do arithmetic, students will be able to figure things out on their own. Nowadays, we have become dependent on their calculators and downloads that we can add from the computers onto the calculators. Sometimes when someone is trying to figure out how much carpeting or fencing and they don't have a calculator handy, they should be able to figure out how to find ther perimeter and area so they can have the correct amount of fencing or carpeting or flooring.