Well, because they won't vote for Trump. Or so the opinion polls show.
Not saying you are wrong to oppose healthcare changes. For myself, I would like to see a public option as the next step.
But first, I don't see the proposed changes happening, so I think you will get to keep your private insurance. It was hard enough to get Obamacare done with a 60 seat senate.
And second, you won't vote for a crook, and nor will nearly everyone else. So Warren would beat Trump if she got the nomination. Vote Trump you destroy what's left of the USA. Even Bernie's policies are not that destructive.