Gee, I need to change a setting on $APP. Wait, is that a config file in /etc/$app/? Or did they put that in /var/lib/$app/? Huh, can't find the setting I'm looking for there, guess I better check /etc/sysconfig/$app...

Usually, developers are sane and put things in /etc. However, there are a number of very common applications which have configurations strewn all over the place. Bonus points for apps which have even additional configurations in their systemd service files!