Writing down moves is a lot of multitasking. My brain has to process what just happened so there is no time to write down moves and especially when I'm down on time.
I've never had any issue with writing down moves (or replaying a game with notation). And I learned descriptive notation in, IDK... 5 minutes? All this stuff is very easy (unless you're really young I guess).
People don't learn to write properly any more. They type with 2 or 3 fingers like I'm doing now.
I learned to type in typing class back in high school. I use 8 fingers (thumbs are for the space bar).