Nano has already supplanted the great EMacs and Vim as the most popular text editor of all linux distros, for though it has many omissions in functionality it scores over the older, more complete programs in two important respects. First, it is slightly simpler; and secondly it has the text "^ Exit" inscribed in highlighted text on its footer
EDIT : This sees to be going over some people's heads. It's a hitchiker's guide to the galaxy reference.
The Hitchhiker's Guide has already supplanted the great Encyclopaedia Galactica as the standard repository of all knowledge and wisdom, for though it has many omissions . . . it scores over the older, more pedestrian work in two important respects. First, it is slightly cheaper; and secondly it has the words DON'T PANIC inscribed in large friendly letters on its cover.
Same reason people use notepad on windows. It's already installed on almost every distro