If you've paid for a specific seat, no social obligation to switch. OTOH I have *offered* to switch my (allocated) middle seat for an aisle to let a couple sit together. Win-win.
But usually I am with the offspring so we have a row of three (me in the middle to prevent squabbles) so it doesn't come up. On a recent trip found our row already occupied. Very politely, I hope, asked them to move back down the aircraft to the noisy bit.
Smartphones: I was a latecomer. But I would not be without one now. Mapping tools are extremely useful. Flightradar lets me know what that aircraft is overhead. Night sky apps mean I can point the phone up to the sky and find out what planet it is. Photos. Video calls. Turn the TV on when we can't find the remote. Control the washing machine when the touch-sensitive panel is playing up. Check rail times, translate foreign menus, check rain forecasts...