I'm an engineer and I use a calculator frequently. I'll use a full computer for more involved calculations, but it's hard to beat the convenience of a calculator that is ready to go immediately for quick computations.
Often a CAS isn't even that useful anyway, they're still pretty shit for any sort of complicated symbolic calculations. As a simple example, even doing basic vector calculus in Mathematica is clunky and barely usable.
Yeah I'm aware, they're just limited. My problem is that they are focused on component-wise manipulation. There's not a good way to do symbolic manipulation of generic vectors/matrices/tensors AFAIK. It's improved though and you can now do some useful things with it- the vector calculus related tools used to be in an external module and truly barely worked.
Edit: the same applies to tensors. Mathematica is actually pretty elegant for working with concrete tensors IMO, but kinda sucks for symbolic manipulation. Not that it's an easy problem to solve. It's like that with pretty much every CAS and I think it will be a while time before we have a good grip on how to do such things with a computer.
Often a CAS isn't even that useful anyway, they're still pretty shit for any sort of complicated symbolic calculations. As a simple example, even doing basic vector calculus in Mathematica is clunky and barely usable.