Parables don’t tell you what to think. They put a small story in front of you and let it do its work. You walk away with something — sometimes the thing the writer intended, sometimes a thing the writer didn’t see and couldn’t have. Either way, it’s yours.
We keep coming back to the form because nothing else delivers a difficult idea quite so gently. A direct argument can be argued with. A parable just sits there, waiting to be ready for.