A biggie you miss is the toolchain: the compiler/binutils/linux-headers/libc/libstdc++ combination. The libc and usually libstdc++ are key components of any install. The other parts usually don't make it to non-dev-desktops, but the distro couldn't be made without them, so they're virtually always available as packages.
Only exception is if the entire distro is cross-compiled or it's made exclusively for containers, but those kinds of special distros break every rule imaginable anyway. Some might not even ship a bootloader or a Linux kernel by themselves.