There could be something to your idea about a failed upgrade, in the
case of an app not supplied by canonical - the old config files could be
incompatible with the new version of the app, whereas a canonical
supplied app would handle the config upgrade as well - but that's not
the common case.

I've been helping people install linux since 1993, and I've never seen a
case where someone installs an app, it doesn't work, and removing it and
reinstalling it fixes the problem. What I have seen is that the personal
config in their home dir can get messed up for whatever reason - and
removing their dot config file or directory resets everything to vanilla
and the app works again.