While fighter pay has always been an issue, fighters were able to make up for the lack of earnings from the UFC with a plethora of individual sponsorships. The UFC effectively killed off individual sponsorships, however, when they put into effect their deal with Reebok in July 2015.
The deal, which made Reebok the official outfitter of the UFC, was quite a lucrative one for the promotion, but it significantly depleted the earnings of fighters. Combatants are no longer allowed to sport individual sponsorships at UFC events or in the cage, and the pay they earn based on the Reebok tier system is leaps and bounds less than what they once did when allowed to find their own partners.
In order to increase not only fighter pay, but fighter treatment and fighter freedom as well, the promotion should seriously consider doing away with the Reebok deal, although that is currently highly unlikely.