Nearly every (relatively) new book about c programming I’ve seen doesn’t seem to adhere to the C99 standard, or they cover it in an extra chapter. Comming from a Java background, the C99 standard made the migration (well, still migrating ^^) much easier for me, and this probably applies to other languages, too.
It seems like C99 hasn’t reached most of the C developers yet. But why?
Short answer: compiler support is slow to get installed and c programmers are a conservative lot who change their behavior slowly.