Because docker-compose had a very bad habit of destroying and rebuilding the volume-only container, unfortunately! This was of course back when running Docker on macOS was somewhat painful, so mounting the DB data directory directly as a volume into your host would nearly always fail to work successfully due to screwy permissions errors (it's quite a bit better now with Docker for Mac)

So, some dodgy code and a JSON file later, and our team uses the `dup` CLI to run everything with exactly zero hitches thus-far, and we've been using (across it's two incarnations) for... 18 months now?