part of the reason for me is that there's less friction to transition from writing to doodling random stuff while thinking about things and going back.

compare writing to typing in a computer, if while typing you start to visualize the concepts/topics and want to do some small doodles while thinking you're kinda out of luck, even if you have a tablet there's still friction and you having to have what's written and what's doodled in separate files.

tablets screen texture still feels less comfortable than plain paper and a ballpoint pen, that why I always have one on my desk.

I almost never return back to my handwritten notes.

I started using a notepad app on my phone a few months ago. I was quite surprised that they supported images and doodling right there in the middle of text. Felt like this could finally compete with pen & paper.