I guess it can go unnoticed, I use Arch so maybe that’s why I got more involved. I remember searching why auto completion didn’t work, then finding out I need to install bash-completions package. After knowing that it makes one curious about how it works. Then the next stage is writing it for my own programs because it obviously won’t come with bash-completions package.

I once wrote a shell (terminal) to watch anime, and I wrote auto completion for different commands on it, it was really nice to just type play then prefix and then tab for auto completion on anime names, and even for episodes I wrote auto completion give me last episode I watched + 1.