Skift has developed an amazing piece on the birth of online travel, collecting stories that help shape our understanding of how we got to where we are today, at least from a business perspective.
At a macro-level, online booking put the traditional brick and mortar travel agencies out of business. There’s still a significant role for travel specialists in high end trips. But there has to be a large margin to cover human intervention in travel, something that doesn’t make sense for basic air or hotel bookings.