The pen acts like an untrained intern. It does exactly what you say and doesn't deviate from that. The computer acts as your manager. It tells you exactly what spot to hit to make a letter.
I'm not sure if this is pure crackpot armchair psychology, but my theory is that some people naturally think on multiple levels and understand things from first principles, and for them UIs are confusing because their brain tries to understand every single thing it sees.
I see "Press button, letter appears, hit the other button to comment" and if I think harder about it "HTML textinput in a form".
They see a lot more and are distracted my questions and don't just expect stuff to mostly work even if they don't know exactly what it does. Maybe at least subconsciously, they are bothered by stuff they don't fully understand.
Like, to me, a file is a "real" thing, with nothing below it that enters my thinking unless I'm reading an article about filesystems. If you tell me about a file, I will probably see file icons and explorer windows in my mind, that's what they look like and that's where they live.
Do people with a natural propensity for first order thinking get bothered at least a little bit by these abstractions? Do files feel less "real" to them? Is some part of them trying to figure out what's going on?
And if they are highly technical, is some part of them wondering what the code looks like, how the text is rendered, or maybe even feeling a sense of self disappointment for not deeply understanding what they're doing?
And is pure old fashioned boredom a factor? If I could see something in my head and then draw it in recognizable form, perhaps I wouldn't see the appeal of vector graphics, if I already knew what point on the paper mapped to what point of the picture in my head, maybe i wouldn't want the overhead of loading up the app to drag points around.
I'd just want to draw it in the right spot the first time, and get better every day at doing that.
And then there's spatial memory. If you have a good memory, the endless tweaks of modern UI probably bothers you. If you don't... Well... The new change isn't any more unfamiliar than the old one because you never deeply learned it!
Digital vs analog is such a completely different paradigm. Analog people are basically working with a blank canvas all the time. With digital you're constantly being led by the machine, and if your mind is overflowing with ideas that the programmer never intended, you might hate it.
If you don't have a deep understanding of how things work and what possibilities there are, you might adore having a framework where you only make small deviations in predefined ways, the possibilities are obvious, right in front of you.
We should probably all do more analog stuff, but a pen is definitely an "Outside the comfort zone" thing for me rather than something that feels like an obvious and natural way to work, aside from simple things we do every day.