And I click on the number digits.
Why?
1. Usually I only click on a few buttons, for example I paste some number, then press / then 2, and then typically ENTER key on the numpad (because I can just press it with the thumb of the hand still holding the mouse). Why should I move my hand from the mouse to the keyboard in order to just press two keys? And then I would also need to check if Num Lock is enabled.
2. I had a phase trying Emacs and Vim and eventually decided I don't care about being more efficient at text editing. I want to edit the text effortlessly, and I find selecting text with mouse, or pressing arrow keys repeatedly, actually requiring less effort from me. Yes, it takes more time, but it's not a time lost, I'm thinking about some problem, and no part of my brain needs to think what kind of text editing function I should use. Likewise, clicking a few buttons in a calculator takes more time, but it's not a race. If I have to make a lot of calculations, I'm more likely to use Excel, so it's rare that I actually type stuff into the calculator.
3. Sometimes my left hand is simply not available (I'm petting my dog or eating something or maybe holding my laptop), and while I have a numpad, using functions like sine would require my right hand to travel. In similar vein, sometimes instead of Ctrl+clicking on a link to open it in a new tab, I just right-click, and choose a context option. It does annoy me slightly, but sometimes not enough to start using my left hand.
You can download a calculator that is designed to your preferences. I actually wrote a calculator in Autohotkey that was a keylogger constantly checking if last typed characters can be interpreted as a mathematical expression - if so, the expression was evaluated and displayed as a tooltip, and pressing a shortcut could be pressed to paste an equal sign and that evaluated value. Never finished it though, demotivated by how hard it was to port to other OSes.
The real draw is the unit support (dates, times, currency, etc etc) but makes it feel natural.
Anything other than day to day use is done via remote connection.
One might want to list the content of a directory without knowing that the magic word is "ls", but there is a 0% chance that someone wants to compute the cosine of a number but can't figure out to type "cos".
And I guess sqrt shortform isn't that common used either.
Able to see symbols can clear those ambiguity
or theres "invisible" calculators like this[1] that do away with GUI altogether. microsoft's onenote has something similar built in as well
The only calculators I know that makes keypad optional/hideable are SpeedCrunch and Qalculate!, and now this.