Collaborating humans have nothing like the problems that require memory barriers. We rarely have anything that behaves like shared memory - shared physical objects might come close, but a physical object is inherently de facto protected by a mutex.

Async, actor-like processes are everywhere in the real world - "something comes into my inbox, I do my piece of work on it, then send it to their inbox". Or "I'll send this off, do something else for now, and then go back to working on that when I get their reply".