The keyword here is "isn't just". It is, but there's more. For example, I use the commandline tool youtube-dl to download videos, but I sometimes also use mpv t

The keyword here is "isn't just". It is, but there's more. For example, I use the commandline tool youtube-dl to download videos, but I sometimes also use mpv to play YouTube videos transparently (it invokes youtube-dl internally). The former use is user-facing, while the latter one is not.