I am not debating whether you should or should not store files on S3. I can see use cases for both using S3 (or some alternate storage).

My point is that - even in the case for django configured with S3 in this docker tutorial, there is absolutely no mention of this. The "dockerized Django" example in the documentation destroys your uploaded files every time you restart the container. Most of the "Dockerizing <whatever you want>" that I have read so far miss the maintaining state part. To me, that is overlooking an important point.