Maybe at least some of this comes down to how people feel about their ability with a pen & paper ? Personally, my handwriting / musicwriting has always been messy (and then got a lot worse following an incident involving a deer, a motorbike and a handful of little broken bones), so I find a text editor much, er, handier than doing it by hand, and scribbling ABC onto a scrap of paper more likely to be legible in a couple of days' time than something involving 5 not-very-parallel lines.