not only an instrument or tool, but a necessity. as the gentleman referred to jazz in this video, you need to learn the instrument or the music will be horrid. typographic care is evident in a good designers work and attributes to both, the rhythm and intuition of good design.
as the famous alex "ajax" jackson once said:
"i was a better designer before adobe allowed for multiple "command z's" (edit undo's) because i had to think about every move i was making."