Problems using cache_dir=$HOME/.ccache: it clutters the home dir when showing hidden files. Also, it slows down utilities scanning the home dir.

Advantages using cache_dir=$XDG_CACHE_HOME/ccache: one less dot-dir in the home directory. Also, makes it easy to delete all cache at once. $XDG_CACHE_HOME/ccache will tipically be $HOME/.cache/ccache

Of course, the configuration file is not cache, so keep reading .ccache/ccache.conf if existing, but favor this as new location: $XDG_CONFIG_HOME/ccache.conf

https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html

(I know I can configure ccache to use whatever cache_dir I want. The proposal is about setting a better default for everyone.)