Imagine the case where you have a project where you added 200 source files, but you never changed a dependency, this is a very common case for more mature projects where adding/updating dependencies is not something you do often.
Using the cache strategy that relies on ${{ hashFiles('**/mix.lock') }}, you will have to compile/generate artifacts for all those source files at every pipeline run, and taking in considerations there are usually at least 4-5 of them for each commit, the penalty for old cache will cost you a lot of time.
