It's hilarious to me how many people deep in tech think they've come up with a new idea but it's literally the entire proposition the new tech destroyed.
And then they 'solve' it by setting up a company that does the same as they used to. But actually they've just destroyed an entire industry and replaced it with a single company that now has a monopoly on everything.
Nah, not true. Travel agencies controlled the access to the booking systems. That was their only role in the value chain. So basically, they would put in your dates, look for options and then make a booking with your detailed info.
Help, guidance, recommendations, curation were MOSTLY off the table. They are and were of course exceptions. But in the end, quality selection IS a new proposition.
In the 80s/90s, travel-agents had a terminal that would allow them to search for and book travel much as one would do with Google Flights/Expedia/Travelocity today. Access to those networks cost real money, so travel agents became middlemen.
Many agents did curate trips (or sell packages), too. In the best case, if your trip went sideways, they could also assist in rebooking/other options.