The author, a Catholic sister, writes incredibly - quite without justification or substantiation - "Why did Jesus speak in parables? In part, it surely put everyone in his audience on equal footing. "

And yet, let's look plainly at the actual words of the Gospel passage she supposedly meditates upon:

"The disciples approached him and said,
"Why do you speak to them in parables?" 
He said to them in reply,
"Because knowledge of the mysteries of the kingdom of heaven
has been granted to you, but to them it has not been granted. "

The passage clearly indicates quite the contrary.   Jesus is treating His disciples DIFFERENTLY than others.

It's not "surely" at all.