It's more like a symbiotic gut bacterium.

A tumor kills the organism within which it develops; a symbiote assists its host in a mutually beneficial relationship, ehancing the chances of survival for both partners.

Regionals provide frequency and cheap feed for major carriers. Unless you can pull off a regulatory hail-mary and require all flying done under a specific brand to be operated by the same certificate holder who markets and tickets the flight, regionals will continue to be the sharecropping peasants on your lordly fiefdom, yielding revenue for the King/shareholders at court.