@Eleanor referred to this in her post #100. I will try to elucidate:
God uses means to accomplish his ends. Your question has been asked by others in many different ways: "Why need the Calvinist do anything, if, elect, he is going to be what God intended all along anyway?", "Why the 'P' in TULIP? Aren't they going to Heaven anyway?", and on and on...
This is typical of the mindset and worldview of those who insist on self-determination. Without realizing that they do so, they attempt to put themselves on even causation with God. They think that what they do
adds to what God does, instead of being
part of what God does.
"Efficiency" is one of God's attributes. He wastes nothing. No act on his part is without effect, and every smallest effect is for a purpose. Thus, when he determined from before the foundation of the world to create a bride for the Son of God, and a dwelling place for the Spirit of God, and a people who together and individually would be with him for the praise of his glory, she being perfect in every way, full of detail and beauty, without spot or blemish, He was specific in what would accomplish this end, He did not "try this and that", but did everything with precision, to include "US trying this and that"—each action on our part with its own effects, to include changes in us. WE HAVE TO choose, do, be active—we can't help it—that much is obvious. But the fact that we do it points to the very creator and sustainer of the universe and of life itself and of very existence. We are not independent of God. Not even Satan is independent.
But look at the earthy, mundane way God has accomplished all he does. Why would we have wills? Why would he create mites and mosquitos? Why does refuse stink? Why does sound travel in the air, at STP, at 1,100 ft per sec? —I'm not talking here as a preacher might, of some poetic way that these speak of God's greatness, but of the day by day not-particularly-important things that have an effect on the hearers of the Gospel, and the doers of God's purposes.
Referring to the example above (the 'P' in TULIP): The perseverance of the saints is by the acts of the saints, by the every day work of the Spirit of God in them, and by external causes on them, by the will of God. It is so subtle that we think WE keep ourselves, not realizing the whole time that every detail is the work of God. THAT is why the perseverance of the saints is a SURE THING. Not because we are faithful, but because God will accomplish everything he set out to do.
So also, God obfuscates the message SO THAT the blind will not see and the deaf will not hear. The SURE FACT that they won't is the work of God. The very principles involved are accomplished by God's direct and indirect acts upon them. They are not independently unable to believe—they are not even independently anything at all. They do not have existence in and of themselves. Satan does not exist independently of God's power. We are mere creatures.