That's what faith is. So that it is known that God alone does it. If there were to objective, empirical evidence that can be shown in repeated experiments that God exists (which there isn't right now, and probably will never be unless God chooses otherwise), then people will believe because of the evidence shown, not because God gives them the gift of faith.
This is a struggle many intellectual Christians have to deal with. Some provide "evidence" by logic. But I believe if I'm remembering correctly, that just proves that a God exists. But it doesn't prove the Christian God of Scriptures.
I have told many a non-believer this: All I have is subjective evidence. I have reasons for believing in God. But I don't have objective evidence. From my understanding of God, I believe that he gave me the ability to believe in him by the gift of faith. From an unbeliever's perspective, I am choosing to believe in the Christian God of Scripture because that is what I want to do.
Hey, you can put your faith in the physical world and all that scientific stuff, lots of people do. I put my faith in the Bible. It's two sides of the same coin (Apologists call both things "circular reasoning". The unbeliever reasons circularly based on things from the world, what the world tells them. The believer reasons circularly from the Bible. Then the unbeliever says that the Bible is part of the world so it doesn't count. That is where we have the disagreement that not everything is from the world: the non-believer thinks everything is and the believer sees that Bible as outside the world, as a revelation of God from the spiritual realm).