The reason Christ himself states that he spake in parables is not the same as what I hear in Sunday School. In fact, ironically, the reason Christ himself says he spake in parables is exactly one of those things that I am taught in Sunday School that “Jesus would never do” because it is so “unchristlike”.
JST Matt 21:34 And again, hear another parable; for unto you that believe not, I speak in parables; that your unrighteousness may be rewarded unto you.
So it wasn’t because parables are a higher form of teaching. It wasn’t some means of protecting people who weren’t ready to hear his message. It wasn’t to reveal, it was to conceal. It was, according to Christ, to reward the unrighteousness of the wicked to themselves.