I’m a physicist so all kinds of numerical and symbolic calculations, e.g. very complicated integrals, differential equations, integral equations, and so on. I also work on math problems either seriously (way back when I was an undergrad I worked on some number theoretical problems where computational insight is very important) or for fun (think Project Euler style problems).
If you just need to a calculator to do everyday arithmetic or unit conversions, or even simple physics calculations with units, it’s serious overkill... I certainly hardly ever need it when I’m wearing my programmer hat.
I guess to answer is that the boundary between a calculator and a full blown computational environment is very blurry to me.