> Why? Who knows! It was never really explained why literally one of the most complex systems imaginable, one that we still really have very little idea how it even works, should be the model for what could and should probably be a lot simpler.

From my understanding, it is that every object has a very limited set of functionalities it manages. And that a goal is for each object to know as little as possible of the outside world. And along with that, to not bind to specific objects/classes but to bind to specific messages (Including multiple dispatch)