Experienced composers and arrangers will have spent years writing on staff paper, building speed and accuracy. This shorthand and muscle memory will be irreplaceable for their target market.

You get a sense of the experience watching the video: quarter notes are just a short diagonal line, all the note stems are perfectly vertical.

In a way, this problem space is perfect fodder for automation. If a musician can sightread off of your chicken-scratched sheet music, the computer will be able to do a decent job too.