Yes, because they have to please the moderates or else they won't win. Progressives are just big enough to tip the scales in a major election against an opponent with a sufficiently energized base, hence the occasional bone throwing. Progressives need to grow their base and mainstream their ideas if they want to have serious sway (see the religious right 1980s -> now). Unfortunately, this process usually happens on a generational timescale, and without the level of conviction that comes from absolutely balls-crazy religious brainwashing, people tend to get discouraged and give up after a few election cycles.