[Brian Swartz]

Because they don't typically have a better idea they can get behind. They don't like the ACA and like the old way better than that, but they don't have a coherent idea on how to do better. The whole country doesn't really. All the polling the last several years that I've seen is that there is a consensus for several things:

** reduced cost,
** keep stuff like portability and pre-existing conditions
** cover as many people as possible, preferably all of the uninsured
** retain freedom of choice within the system
** modest increase in taxes at most, preferably no increase
** continued high investment in new research etc., to Arles point

The problem of course is that you can't do all of those things at once, and people aren't generally willing to give on any of it, so while public opinion is trending towards single-payer there's not strong agreement on any remotely realistic option. It wasn't until a couple years ago that we got to the point where there was a clear majority in favor of single-payer - a decade ago that idea was significantly underwater. And even within that agreement, once you get into the details the consensus fractures badly.