But at that point you've reinvented mainframe-like terminal interfaces. "Everything old is new again", but is that good?
The public can 100% manage and love terminal interfaces... as long as it looks like a text message.
Now, with my google assistant? Text interfaces are awful, because I have no idea what combination of magic words will confuse it. What will be interpreted as a parameter to which command. Even simple commands get broken if I accidentally add phrasing where it interprets it as a different command... usually just giving up with "I don't know how to do that" and then Google gets a nice recording of elaborate cusswords.
I think speech recognition is good enough for this, but what is left is making a complex tree. See the 20 questions game where because so many people have put in new answers it now can guess almost everything after just a few questions. This is not easy and it takes a lot of effort to figure out where things didn't work and fix it so it will for the next person. At least some of those things you fix will never be asked again, but you need to do it.
Part of the above is speech recognition needs to expose a confidence and if it thinks it knows ask useful questions about what you mean. (they already do in some cases)
This is why I love chat-with-a-human interfaces on websites for support (although they mostly require maintaining browser state) because staying on a phone line absolutely sucks and the person helping you also doesn't have a real-time constraint so they often have the ability to get you better answers to hard questions.
Every "natural language" system, whether it's a text chatbot or Siri-style voice bot, is essentially a command-line interface without very good documentation.
In general, it was considered an advancement over the classic CLI (at least for environments where there's low expected user proficiency) to provide a menu of valid choices and put them front and centre.
Most customer service scenarios are exactly that-- low user proficiency (in company- or business-specific terminology, or sometimes even the very transaction flow itself) so they may not be able to quite enunciate exactly what they mean, but can easily pick from a clearly written menu.