What is true is that all Christians believe in divine sovereignty, but some are not aware that they do, and mistakenly imagine and insist that they reject it.
What causes this odd state of affairs?
The root cause is the same as in most cases of error in the church -- the intruding of rationalistic speculations, the passion for systematic consistency, a reluctance to recognise the existence of mystery and to let God be wiser than men, and a consequent subjecting of Scripture to the supposed demands of human logic.
People see that the bible teaches man's responsibility for his actions; they do not see (man, indeed, cannot see) how this is consistent with the sovereign lordship of God over those actions. They are not content to let the two truths live side by side, as they do in the Scriptures, but jump to the conclusion that, in order to uphold the biblical truth of human responsibility, they are bound to reject the equally biblical and equally true doctrine of divine sovereignty, and to explain away the great number of texts that teach it. The desire to oversimplify the Bible by cutting out the mysteries is natural to our perverse minds, and it is not surprising that even good people should fall victim to it. Hence this persistence and troublesome dispute. The irony of the situation, however, is that when we ask how the two sides pray, it becomes apparent that those who profess to deny God's sovereignty really believe in it just as strongly as those who affirm it.
How do you pray then? Do you ask God for your daily bread? Do you thank God for your conversion? Do you pray for the conversion of others? If the answer is "no," I can only say that I do not think that you are yet born again. But if the answer is "yes" -- well, that proves that, whatever side you may have taken in debates on this question in the past, in your heart you believe in the sovereignty of God no less firmly than anyone else. On our feet we may have arguments against it, but on our knees we are all agreed.
Extract from Evangelism and the Sovereignty of God - J. I. Packer