"Pen paper and calculator works."
Yes, it should do. But it doesn't.
I can't remember the last time I was provided with a copy of somebody's army list that was hand written.
But I can remember many, many times playing against people who "Know Their Army So Don't Need A Written List" and after the game finding out that they've fielded around 20% more points than they should.
And I can remember many, many times when I've handed an opponent my printed list and seen them instantly tailor a list to combat what I've brought and declared.
Personally, I normally have two copies of my army list printed in advance, one of which is for my opponent to keep as a reference during the game and to take away and digest after the game if they so wish.
Anything that promotes open and fair play should be commended.
Though I take your life, I promise you the stars...