Not becasue they care about the plan or whether it may benefit their own constituents, but only because they are against republicans/conservatives.
I suspect the AARP leadership will fight tooth and nail against fixing what member$ perceive is not broken. Doing so is a lot easier and less risky than attempting to persuade those member$ that it's a good plan.
Whether or not they succeed in stopping the plan, if they can convince their member$ that they're looking out for the member$' best interests, everyone will be happy.
"Let the kids worry about their own retirement (while they pay for mine); keep your politician paws OFF."