The request isn't about macros calling other macros. It's about macros placing macros on a hotbar.

This isn't a situation where you press 1 and you loop through infinite abilities.

It's where you press 1 and a slot somewhere on your hotbar changes. You still have to hit that button to get the macro you've just placed in it to fire.

And, like OP said, you can already achieve exactly the same effect by switching/copying hotbars back and forth. It just takes up a ton of hotbar space and is much more of a pain to work with than it would be letting macros assign macros to individual hotbar spaces.