Have you tried? I used to draw, a lot. As much as this guy but I was a lot younger. People often told me the same thing "I couldn't even draw a cup that looks like a cup!" Sometimes I'd get them to try and if they were a little bit patient they drew something that looked a lot like the first drawing of that mug (Usually not including the shading).

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.