It has much slower startup than a typical calculator (which can be <0.1s on a modern system), also installing Julia just to get a calculator is probably overkill.
Which is fine, it was not meant to be a calculator, but a very advanced programming language. The fact that one can use most modern interactive languages as “calculators” does not mean that they are the best tool for the job (unless, of course, one already uses them for something else, probably programming, then availability & familiarity are dominant aspects).