ncurses-base and ncurses-bin are marked "Essential" in Debian (from which Ubuntu derives, and automatically imports packages), which means that any package is permitted to depend on things in those packages without declaring a dependency - including in pre-installation scripts. This image is defined as being large enough that any package in the Ubuntu archive can be correctly installed.
You could eliminate this by going through and finding all packages with implicit dependencies on ncurses-bin / ncurses-base, but that seems highly unreliable, and also a huge amount of pain, since Debian probably will not want to drop these packages from Essential (so you will end up maintaining a huge Ubuntu diff).
I could also imagine a scheme where packages in Ubuntu main are scrubbed for these sorts of implicit dependencies, but packages in Ubuntu universe (which is where auto-imports from Debian go) aren't, and apt-get automatically pulls in all Debian "Essential" packages as soon as you try to install something outside main. But that's a good bit of dev work and it's not clear that you'd get a meaningful payoff.
(update-motd.d is from base-files, which is also an essential package, and is actually important; again, possibly Ubuntu could carry a patch to split up base-files, but for < 1kb of text files, it's unclear this is worth doing)
You could eliminate this by going through and finding all packages with implicit dependencies on ncurses-bin / ncurses-base, but that seems highly unreliable, and also a huge amount of pain, since Debian probably will not want to drop these packages from Essential (so you will end up maintaining a huge Ubuntu diff).
I could also imagine a scheme where packages in Ubuntu main are scrubbed for these sorts of implicit dependencies, but packages in Ubuntu universe (which is where auto-imports from Debian go) aren't, and apt-get automatically pulls in all Debian "Essential" packages as soon as you try to install something outside main. But that's a good bit of dev work and it's not clear that you'd get a meaningful payoff.
(update-motd.d is from base-files, which is also an essential package, and is actually important; again, possibly Ubuntu could carry a patch to split up base-files, but for < 1kb of text files, it's unclear this is worth doing)