Why does Jesus speak in parables instead of ‘telling it plain’?

First,  speaking in parables allows people to find themselves in the story, not just in the moment, but across millennia!  Second, Jesus says that He speaks in parables as a kind of code for the insiders.  For persecuted groups, this can be an important thing to do, to protect from the powers that oppress them.  This is more necessary for groups that are doing things that will upset the balance of power.  What is Jesus up to that is so disruptive?
-Pastor Trudy Stoffel