Because he has a lot of experience in one very specialized area of programming which very much doesn't reflect the wider profession. It's the same problem as e.g. http://codon.com/the-dhh-problem
I'd recommend beginners listen to a wide variety of "big names", but only those who are clear about the scope and limits of their experience.
I'd recommend beginners listen to a wide variety of "big names", but only those who are clear about the scope and limits of their experience.