I can only vouch for what happened in my life. I grew up in a devout Catholic tradition. We never missed a Sunday or Holy Day of Obligation Mass for we were taught to do so was a mortal sin. We attended Mass and prayed through the Rosary daily during the Lenten season. I served as an altar boy, sang in the choir, attended Catechism classes, and attended Catholic school. Every evening my brothers and sisters and I knelt on our living room floor to say our prayers before going to bed. The 10 Commandments were strictly taught and adhered to. To this day (I'm 61) I can attend a Mass and still recite nearly the entire Liturgy from memory including the Priest's words.
What happened? As I entered into my later teens I began to question some of what I had been taught. Of particular impact for me was the subject of prayer.
In all those years I was never taught what prayer really was... a conversation between me and God directly. Prayers were always these formal penned statements and except for the Lord's Prayer, never addressed God directly but instead addressed those the Catholic hierarchy identified as saints, asking for their intercession. When I read Scriptures like Isaiah 53:12, Romans 8:26-27, Romans 8:34, and 1 Timothy 2:5 I began to understand that there is but one intercessor and that is Jesus.
When I attended confession and after performing absolution the Priest assigned penance in the form of repeated prayers, such as 10 Hail Marys and three Our Fathers, and this too began to raise a lot of questions in my mind. First, it reassigned the purpose of prayer as a form of punishment (penance means punishment) and secondly I began to realize that it flew in the face of Matthew 6:7 about praying with vain repetition.
I began to see those prayers and the Liturgy (which I now believe is a prayer) as nothing more than mere words repeated from memory with no meaning for me anymore. It just happened that these things began in my later teens and about the same time I was entering college. This is a time in our lives when we enter adulthood and we start to think more for ourselves, exploring and learning more of our individuality. My confusion then led me to leave the Catholic tradition and unfortunately I also left any belief in God. It wasn't until I was nearing 40 before I began to become aware of God's presence in my life again through the help of some neighbors and our small country Lutheran church.