From what I've seen, for a lot of people it's just the... reprogramming of instincts to look at the screen while drawing rather than your hand. Now, after drawing with a (wacom) tablet for fifteen years or more, it's completely intuitive.
Doesn't mean my art is uber-fantastic, but I still like using it. And I'm still regularly learning new tricks for the drawing programs I use, so that's fun, too.
(And you inspired me to do the 10k drawing challenge. I started June in 2015, and just crossed over 900 images this week. :x )