This is very wasteful. On servers in the cloud that may be a reasonable approach, but there are still devices that are memory, storage, and/or network constrained enough where it's not. It's still necessary to have relatively stable interfaces such that most things can share the same version of a dependency and their still exists the ability to deduplicate the dependencies between different programs. I do agree that the current OS approaches to handle this are not great and there is room for new models, but docker containers are not a holistic solution.
The Windows Component Store (aka Side-by-Side aka WinSxS) is sort of a content-addressed store for DLLs and the like, except the content-addressing isn't facilitated by a literal cryptographic hash over the contents, but instead by the logical identity of the component (name+version but more). And, it doesn't fetch anything automatically. Writes to certain paths are just intercepted and redirected into it, while storing an association somewhere else that the app that did that (or was installed doing that) wants that particular component (or at least, that's how I think that works).