"I do, at least for three or four days ahead, and only rarely now a week. I've been doing so since I was 19 years old, using the same highly reliable technology: primary storage is a piece of paper kept in my back pocket, augmented by a non-hackable input device known as 'the nearest pen or pencil'.
Admittedly, after three decades, the secondary storage wetware is a tad less reliable than it used to be..."
Trouble is, that's not as reliable as you think.
Paper kept in the back pocket? Oops, fell out when you sat down and you didn't know it, or you slipped in heavy rain and fell on your butt. Jeepers, paper's all soaked and runny; can't make anything out. And other times, you may just forget it when switching pants.
Pen or pencil? Stepped on it, rolled off the table, got chewed by the dog, stolen by someone else, point breaks, lost it.
And I speak for ALL of these FIRSTHAND.