But why, when they are that profitable, do they need a government subsidy in the form of a royalty waiver?
Because the royalty waivers were part of the incentive that got them take the Exploration/Production risks in the first place. The waivers were granted during the Clinton administration (the stain got one right).
Between '97 and '99 crude prices dropped to between $10 - $15 per barrel and slick was trying to use the incentive to keep US companies in the exploration business.
Are you saying that because prices are up now the rules should be changed in mid stream?