> Why does the size of a base image matter? What happened to the shared layers between images?
It matters because when bootstrapping new hosts you still need to download all the base images, and because in many systems the base images can come to totally dominate the storage needs.
It still can often save a lot, but it's not enough for a lot of places where people want to use Docker.
If you need a library, you will download it anyway. But you can download it once, in base image, or multiple times. IMHO, the fatter _base_ image is, the better.
Ideally, base image must be full installation of everything, one large image for all. You will just download it, and it will just work.
It matters because when bootstrapping new hosts you still need to download all the base images, and because in many systems the base images can come to totally dominate the storage needs.
It still can often save a lot, but it's not enough for a lot of places where people want to use Docker.