The original Emacs was written for Multics at a time when people outside of Bell Labs were largely unaware of the existence of Unix[1]. It also doesn't follow the Unix philosophy of making small CLI utilities composed with pipes. As I understand it (though I haven't used it), Acme is extended with external programs which communicate through pipes just like the traditional Unix utilities.
[1]: https://www.jwz.org/doc/emacs-timeline.html