> Some people work with code from 13" laptops. And viewing diff of two files of 79 char per line max becomes very convenient. I think it's not the only reason.

> Some people work with code from 13" laptops. And viewing diff of two files of 79 char per line max becomes very convenient. I think it's not the only reason. Limiting columns forces developers to read more vertically, which is less tiring for eyes. For example, try to read a book on a 27' monitor with no max width. Going to the next line will quickly become painful.