A couple of questions related to image content

My experience in docker-related stuff is limited (I do not know best practices yet), but I see some things that make me doubt, and I want to raise them.
* 2 packages (curl and GnuPG) are left in the image. Is there any reason behind that?
* I see an `apt clean` call, which takes care of `/var/cache/apt/archives/*`, but I do not see anything that takes care of the lists (`/var/lib/apt/lists/*`) we downloaded previously (through `apt update`). I guess that it would be nice to take care of that.
* We have an `apt update` but not an `apt upgrade`, which means the base system will not be up to date. Is that okay?
* If we are going to do an `upgrade` it would be nice to run also `apt autoremove --purge` somewhere near `clean`. I admit that the chances we wipe something useless are really low, but I think it's good to be sure we are good there.
* it also seems like `get-pip.py` file will be left in the image's FS. should we juggle with stdin/stdout?