Why? It is part of their strategy to institutionalize the program to the extent that it cannot be repealed, or so they think.
I am sure McCain agrees with their goals and purposes or he would have joined the majority of his party in making the repeal of ObamaCare the key issue in the debt ceiling debate. 162 Republicans in both houses of congress voted with Ted Cruz, Rand Paul, Marco Rubio and Mike Lee while McCain and his defeatest RINO Herd, all 116 of them, voted to support Obama and the other Progressives in D.C.
Understand and believe this: when dealing with liars and deceivers, actions define their true motivations to the exclusion of their words.