[diarrhea]

`ls` doesn't have a 'parent' in the hierarchy. `exa` does, it's `ls` itself, so there's a fallback. When there's no fallback, it cannot be deprecated; there's nothing to use otherwise. So it's either kept alive or forked indefinitely.

[sanderjd]

`ls` does have a 'parent' in the hierarchy: the system calls used to implement directory listings. If `ls` were deprecated (eg. if GNU decided to deprecate it and GNU/Linux distributions actually decided to go along with that), then you or someone else would need to write a new implementation using the system calls, in order to have a useful system.

[anthk]

    man 2 stat 

it's not rocket science.