That is probably true for most of them. But it is still very worth his time to do this. Hillary treated them like they owe it to her to vote for her. Trump is sincerely asking for their votes and treating them respectfully. He may not win many of their votes, but he makes Hillary look even worse. It is one more contrast between them where independants can be convinced he would be a better president for all citizens than Hillary, who takes her support for granted.
Trump may also succeed in showing them how enough of the lefty promises are only will-o-the-wisps, that they may change their minds.