But unfortunately they also become very space inefficient when a lot of processes need the same (relatively) large blocks of code. But if you carefully curate your containers to use the same base image that contains those libraries already, you don't have to duplicate it.

Comparable would be to having an inode de-duplicating file systems, and deterministic binary generation. But it's hard to prove "the correctness" of inode de-duplicating file systems in extreme environments like auto is required to, and deterministic binary generation is hard to control 3ven if it is possible with the specific build tools (it usually isn't).