(because left hand is on the keyboard, and right hand is on the mouse or stylus, and putting down the mouse to reach for a numpad is just weird.)
Doing it with the laptop would be even worse, I imagine.
However, I think there are use cases and people who prefer using them. Some software is really geared around the full cluster being there. I've got a full size, numpad-ed keyboard (some old stock DEC thing that went to a mid 90s alphastation I believe, I got it for dirt cheap) attached to my "windows gaming machine", and I use the numpad on a few shortcut-heavy games.
Otherwise, though, I just don't have any muscle memory for it. I have to look and hunt/peck for keys on a numpad. I'm mostly using bash and vim for work, though...
Now I feel crippled whenever I'm on my laptop, which doesn't have a numpad, my own fingers flailing uselessly over numbers that whilst in mind are not available to my right hand.
I should probably get one of those external numpad USB things, but I much prefer a whinge.
This includes a surprising variety, from accountants and POS, to 3D modelling artists...