Pure math people probably don’t reach for calculators. But engineers do all the time. Back of the envelope guesstimating is bread and butter.

The modern equivalent of a calculator is Excel.

> Back of the envelope guesstimating is bread and butter.

And that is not done with calculators, that is done quickly in your head by having practiced a lot of calculations manually. This is why engineer students still practice manual calculation in college in most places.

Calculators are taken for granted but many mathematicians use computers extesively in their careers.