It's because they're a phony opposition. Every single Republican in the Senate ran on the premise that Obamacare will be a disaster and it must be undone, yet they have since then resisted any effort to fight it beyond simple up-or-down votes that were foregone conclusions.
You see, the GOP exists for one major reason. They exist to be the default vote getter for conservatives, to corral our votes so that they can then be shoved into storage. People put together one last impressive groundswell in an attempt to reform this party, since it was the expedient vehicle to try and counter the Democrats. But this party is simply unsalvageable.
They are banking on people just becoming disgusted and/or fatigued by the whole thing, throwing up their hands, and letting our Ruling Class be actual rulers. I have no intentions of acquiescing to these sh*theads. If Going Galt is the only thing we have left, then so be it. In the meantime I will do everything to spoil the GOP, up to and including voting for Democrats. Like it really matters anyway. It might mean we become a full blown Democratic Socialist state, but I will luxuriate in the schadenfreude that the GOP is dead and buried.