There may be more than one airline, but quite often there is just a single airline that meets the criteria for the flight and service quality you require. Even

There may be more than one airline, but quite often there is just a single airline that meets the criteria for the flight and service quality you require. Even when there are competing companies, being able to accurately quantify how much are you willing to pay, would allow companies to always charge max price, just by setting their "normal prices" much higher and then offering you personalized "discounts". With multiple companies buying your data from intermediary brokers, it would effectively become a way of per-customer price fixing, while at the same time reducing competition when only a single company gets your data and presents you with an offer you can (barely) accept.