It's because we all have different expectations and use-case. A PDF is great if you need to ensure the formatting looks the same on all platform, while HTML and

It's because we all have different expectations and use-case. A PDF is great if you need to ensure the formatting looks the same on all platform, while HTML and its derivative (ie: ePub) are useful when you have a myriad of display size where you want the text to reflow and maximize the screen usage and readability (font size, etc) without caring too much about the layout.