Doesn't go far enough for file servers

One word explanation: ls

Multiple word explanation: It's a question of simplicity, I suppose. This way you avoid introducing more concepts and tools. Notice just how simple it is to say "every link can have different permissions". Compare that to the simplest explanation of POSIX ACLs.

Additionally, you don't need to modify existing tools, and hardly add any new ones. The only one you may want to add is something that gives back the list of aliases (links) to a file.

In return for that simplicity you have to give up on the expectation of absolute ownership. You no longer can revoke permissions on other's links, but you can always recreate a file.