His initial drawing are much, much better than anything I could currently muster.
I'm fairly confident that most people could draw that first mug if they really wanted to. The drawings 30 pages in though, that takes much more skill and patience. And it takes a long time to learn it.
Obtaining the rest is just time and passion.
But many people waste a lot of the time they do have in their life -- playing mindless games, reading/watching absolute trash, surfing the web or any number of other absolutely useless activities.
It's very difficult to really dedicate yourself to getting better even at a single skill over many long years. There are always distractions and a lot of boredom and self-criticism to overcome. It's painful and hard, and many people just don't have the willpower to do it.