We are talking about things to do on a plane seat.
The last (and only) time I did a long distance flight, I did 3 things: I watched movies (using plane hardware), I slept (badly), and I used my laptop (I played and worked a bit).
Without my laptop, I could only watch movies or sleep. With a paper notebook, I could do some work, but not much. I could also talk with my neighbours if they feel like it.
Also, I have reserved a flight this summer to see the eclipse. There's no way I'll let my laptop in the cargo hold, for 2 obvious reasons (theft and accidental destruction). So, no laptop for the entire trip. I'll guess I'll have to make do with my palmtop. Not great.
And this is a leisure trip. For a business trip, I would need a computer with my personal settings, that I'm used to: custom keyboard layout, unusual window manager, a GNU/Linux OS… Borrowing a computer can easily be a major hassle.
Asking everyone in a plane to have nothing to do during a 8h flight (at best) is not a "minor inconvenience".