The will of God is as singular as He is One. Jesus implies the unity of the divine will between the Persons of the godhead in numerous places in John's gospel, Jn.5:30; 6:38; 10:30; 15:26; 16:14-15; etc. Therefore, there is no disjuncture between the purposes of Christ in his teaching, and the Spirit's activity in application. Our starting point is internal divine consent.
We accept there is value in the method Jesus chose to teach publicly, a preference we may in some ways (but not others) be able to grasp by further listening and meditating on what is revealed. One reason is surely: in order to fulfill prophecy. But why is it so prophesied that he would come speaking obscurely? On the face of it, the method of parables itself (leaving aside the content for now) assumes a certain amount of work, of engagement, is the duty of the hearer. "Is there, shouldn't there be more here from this powerful preacher than clever stories? What am I missing?"
Paradoxically, the parables of Jesus are at the same time illuminating to those who have eyes to see, and dark sayings to others. The same idea may be found in other cases of literature or media, minus the spiritual quality. Some people just go to a movie, and either enjoy it or not on the basic, storytelling level. Don't bother them with artistic depth, multilayered messaging, or philosophy. But for a certain class of moviegoers, awareness of factors beyond the superficial give them greater appreciation for the presentation. Honestly, they get more out of it; and the reaction of some in the first class to hearing what the second class thinks is derision, or indifference, or confusion, even anger that some people think they got more out of the experience. Just a few of them may be intrigued, and take for themselves a new step down the cinematic-appreciation path.
I'm not equating a movie director, or a master painter, or a brilliant author with the Savior, who taught powerfully through oration; merely pointing out that Jesus did not invent the parable, nor did he by his speech infuse his words with some kind of selective "spellbinding" that put him in a category of one, ahead of all other orators. Jesus used the common speech, the common language, recognizable and relatable forms. The world wanted, and still wants a hero of glory, a gleaming knight on a white steed, a king at the head of an army, a wizard with charisma, a rhetorical genius with scintillating phrases and dizzying range. Instead, God sends them one who projects no extraordinary outward quality (Is.53:2), who is not "head and shoulders" above the rest (cf. 1Sam.10:23), but who is uncharacteristically gracious (relative to other men).
Jesus' parables are drawn from ordinary life, and he masterfully employs them to great effect, able to impress people of all ages and stations. Because the Lord isn't after a certain "class" of people, or those having a native gift. His parables (and all the rest of his teachings) thus work in tandem with the labors of the Spirit, who brings degrees of light (or shadow) to the minds of them that encounter the living Word.
Some people would prefer Jesus spoke in an even more simplistic manner, as if the only way to surely convey truth is to use one or two syllable words, and short declarative statements. Others would prefer Jesus spoke in a more elevated style, using big words for his big ideas, the better to impress the intellectual and well educated (and who cares for the simpletons left behind?). Jesus' use of parables subverts both of those expectations, while at the same time calling on all hearers to "love the Lord your God with all your... mind."