Your example is a great example because the secretaries are clearly filling in the gaps, such as
1. How much can you spend on this trip?
2. Is first/business class necessary?
3. Is a layover acceptable if it's cheaper?
3a. Is it better to have a 4am flight nonstop or a 7am flight with a layover?
4. Are there preferred airlines?
5. Are there preferred hotel chains? What's the hotel budget? Do you want to pay extra for a nice view?
6. What kind of car should you rent? Is there equipment you'll be handling?
etc...
This is the kind of stuff that's easy(-ish) to communicate by presenting a list of options to a user through an actual interface. It sucks doing it through voice; think of the old phone systems where you had to go through droning "If you would like to rent an SUV, press 1. If you would like to rent a sedan, press 2. To speak to an operator, press 0."
So no, you never had a voice interface for booking flights; you had a human brain to whom you delegated, which is very different.
This is interesting to see from multiple sides. The method (voice/chat/whatever) is one piece but the other is:
You already show many questions on one issue (a ticket).
Would you need to think about those? With the secretary the task is split: you decide you need the ticket, the secretary handles the rest while you focus on what you do.
Presenting all options, getting all callbacks, confirm e-mails etc does not change that. It puts all load on you.
1. How much can you spend on this trip? 2. Is first/business class necessary? 3. Is a layover acceptable if it's cheaper? 3a. Is it better to have a 4am flight nonstop or a 7am flight with a layover? 4. Are there preferred airlines? 5. Are there preferred hotel chains? What's the hotel budget? Do you want to pay extra for a nice view? 6. What kind of car should you rent? Is there equipment you'll be handling?
etc...
This is the kind of stuff that's easy(-ish) to communicate by presenting a list of options to a user through an actual interface. It sucks doing it through voice; think of the old phone systems where you had to go through droning "If you would like to rent an SUV, press 1. If you would like to rent a sedan, press 2. To speak to an operator, press 0."
So no, you never had a voice interface for booking flights; you had a human brain to whom you delegated, which is very different.