I believe the following from Southern Baptist pastor, author, and blogger Joe Thorn concisely and cogently explains why we need Confessions of Faith:
“For twenty years, I have considered myself a “confessional Christian.” That means I subscribe to a historic confession of faith that I believe beautifully and accurately summarizes the Christian faith. This doesn’t surprise people who know me. I tend to wear my convictions on my sleeve. Literally. The tattoos that cover my chest and arms speak to the faith I hold dear. The tattoo on my hand reads “1689” for the 1689 Baptist Confession of Faith.
Because I love God, I love his word. And because I love God and his word, I love theology. And because I love theology, I love confessions of faith. To know God is to believe who he has revealed himself to be in Christ, to rest in his grace, and to obey him in faith. In all of this, we are dependent on the Holy Scripture, and are compelled to affirm and articulate the truths revealed therein. This is where confessions of faith play a vital role in the spiritual health of the Christian and the local church. (full article here)
In the above excerpt, Mr. Thorn says, “The tattoos that cover my chest and arms speak to the faith I hold dear,” which is really the purpose of our Confessions–they speak to the faith we hold dear.
And even those who “confess” that they have “no creed but the Bible,” when you ask them what they believe about the presence of Christ at the Lord’s Table will tell you what they believe, speaking from what they hold dear.