This is a nightmare for people who produce actual print materials. My SO is a print designer doing mostly packaging design but also does some trade show materials. There is an incredible amount of thought in layout that can almost be considered branding for a company. Additionally, the static nature of print allows you to do complex layouts that wouldn't be translatable to HTML, let alone support different rendering engines, browser sizes, etc.

Many times even things like page or column breaks are extremely intentional. Having something "beneath the fold" or flowing onto another page can drastically change the way someone interacts with the piece of media. No PDF isn't great (my particular beef is with how there's almost no sense of a sentence, block, paragraph etc so it makes it almost impossible to copy or parse for text), but keep in mind that HTML/CSS only just reached near-parity in features in the past 5-6 years.