High barrier to entry, consolidation, and collusion. Look at how many airline mergers have happened over the past decades.
Most people want cheaper tickets and don't shop on quality. In the rare cases that they do airlines readily adjust. But the airlines trying to offer quality as the default would go out of business
Basic economy doesn’t exist because of Google Flights. It exists because it sells. Well enough that it sustained entire discount airline fleets until the majors copied their model.