The end goal is not letting the airline cancel the ticket of the lowest paid passenger when they overbook, for one example. An efficient market simply doesn't serve the people who can't pay enough to be attractive customers: it makes poor people either pay more or not fly. It can also change those rules on the fly by e.g. cancelling flights without enough passengers booked, or selecting the person with the lowest value customer profile to bump when a flight is overbooked.
Regulations are usually introduced when people realize that the very efficient corporate choice like 'cancel underbooked flights, sell as many tickets as we can for each flight and bump the lowest paying passengers at boarding time' really screws over passengers. In the US, this is accompanied by giant waterfalls of public money being spent on the infrastructure required by airlines to cover the overhead that is mandated, like airports and air traffic controllers.