The first reason, as Noel Piper writes in chapters 3 and 4, is that they teach our children about God - who we know through his acts and words.
We are always teaching our children, whether intentionally or unintentionally. They will notice what things are important to us, and what things aren't. They will quickly notice what our greatest treasure is through their observance of our actions.
Intentionality will take planning. Like Piper, I've found that if I don't have some sort of plan to teach my kids about God through repeated events in our lives, then they'll receive a 'burst of God-talk for a day or two' which will quickly die down. But children learn (as Piper points out in chapter 4) through repetition, regularity, consistency, so it's important to have structures in our days and weeks and years that enable us to teach them about our God.
Then there are the unintentional ways we teach our kids too. I loved what Piper had to say about this:
Alongside that intentionality, there is also the unintentional aspect of teaching. When God is part of our everyday conversation and habits and life, we realize that while we are teaching particular things with our words, we are also teaching by our lives things that can’t easily be put into words. The specific “truth jewels” we lay in our children’s hands will, we pray, be stored in their hearts' treasure chests; and the gems will be protectively surrounded by packing material, the wad of impressions, feelings, and assumptions they’ve picked up, both consciously and unconsciously, of who God is and what it means to be a family.There is another reason why I think family traditions are important, but I'll deal with that in the next post (on Friday).
The factory for that packing material is our everyday lives. Our “everyday” traditions are the purposeful, significant activities that we do most frequently and regularly, the things that give shape to a day and a week.