The portrait orientation notebook

Webpages are vertical. Pages are vertical. Most of my images are vertical. Why are notebook screens horizontal?

A conceptual rendering of a vertical screen Macbook Pro
A conceptual rendering of a vertical screen Macbook Pro

Webpages are vertical. Pages are vertical. Most of my images are vertical. Why are notebook screens horizontal? Most of the time, my browser window only takes up 3/4 of the screen. Wouldn’t it make more sense to at least offer a portrait orientation notebook? The only thing I can think of that must be horizontal are movies but I didn’t buy a notebook to play movies. Even if playing movies is required, it can easily be solved with a rotating screen such as the one in this HP Touchsmart.