Cuz not all people accept the free gift God offers, some would rather have dung covered candy and other false gospels.
All of Grace: C.H. Spurgeon
Sunday Morning Sermon
There can be no present salvation unless it be upon this footing"By grace are ye saved." The works being unfinished, the salvation would be incomplete; or, the salvation being complete, the main motive of the legalist would be gone.
Salvation must be by grace. If man be lost by sin, how can he be saved except through the grace of God? If he has sinned, he is condemned; and how can he, of himself, reverse that condemnation? Suppose that he should keep the law all the rest of his life, he will then only have done what he was always bound to have done, and he will still be an unprofitable servant. What is to become of the past? How can old sins be blotted out? How can the old ruin be retrieved? According to Scripture, and according to common sense, salvation can only be through the free favour of God.
Salvation in the present tense must be by the free favour of God. Persons may contend for salvation by works, but you will not hear anyone support his own argument by saying, "I am myself saved by what I have done." That would be a superfluity of naughtiness to which few men would go. Pride could hardly compass itself about with such extravagant boasting. No, if we are saved, it must be by the free favour of God. No one professes to be an example of the opposite view.