I keep notebooks still for most things. I use them to jot down ideas, sketch out designs and just generally write down my thoughts so I don't forget them, I usually have one to many per company and one per project. I also use them to take notes in meetings versus trying to take notes on my computer in real time. Personally, I find it pretty rude to be typing away on a computer while people are presenting or we are discussing ideas. It seems far less rude to jot down notes on paper and then come back to it an flush things out after the meeting.
I do translate my notes as I work through the problems and put them in a tool like OneNote or Evernote etc. But I always start off with sketches and notes in a notebook. My bet is if you looked at the pattern of those who use notebooks vs those who don't, you'd find those of us using notebooks still skew to an older average age. 40ish+ likely.
Personally, I also jot down pseudo code on paper to get my thoughts right before starting to code the problem. This lets me get my thoughts straight before coding it and I find I make fewer mistakes, plus I am faster when I do this. It is also one of the reasons I dislike coding interviews where someone wants you to just start writing code in the IDE. I don't do that well, because to me the process is, understand the problem, design the solution, engineer the solution, then start coding.