If you run two jobs right after each other and the machine tries to pull the image separately for each one and redownloads the whole thing, then that's a poor cache. Modern practices make this relatively easy to accomplish by accident.
Especially for Docker, which is typically a daemon that runs in a different execution context as the CI job, which means you cannot just tell the CI job to cache some directory. Podman makes this easier but isn’t used as widely as Docker is.
a sibling comment to yours[0], from 'treesknees, addresses what a decent caching setup for this looks like.
> We've since started caching our images locally using Sonatype Nexus Repository Manager plus hosting our own registry for some simple things we used to be pulling from Docker Hub.