Laptops and desktops are (almost) always in landscape mode, don't have to deal with virtual keyboards occasionally taking up large parts of the screen and have

Laptops and desktops are (almost) always in landscape mode, don't have to deal with virtual keyboards occasionally taking up large parts of the screen and have subtly (and not so subtly) different use cases. I agree with the point that content providers adapt but it's not a case of what's right for one type of content, it's what's good for one type of content on a specific device type, possibly in a specific situation. (Worth noting that Apple certainly don't believe 4:3 is some universal "right" ratio - the iPhone 5 is 16:9 as are Macs, 4:3 is only the aspect ratio for the iPad)