Once upon a time, Hazel sewed her family's clothes. She lived in an era when there were no department stores or major clothing labels. And Hazel's family couldn't afford the services of the nearest tailor, so Hazel sewed because that's what was necessary to survive. And because it was necessary to survive, Hazel taught this skill to her daughter Sarah.
When Sarah grew up and had her own family, she found that this skill was no longer a necessity. For a reasonable cost, and with the aid of a department store or a catalog, she could contract someone else to do the hard work of measuring and cutting and stitching. But even though she didn't need to sew anymore, Sarah still pulled out the Singer from time to time. She'd sit down with her daughter Kimberly in her lap and make a garment or two around Christmas. Sarah did this because the feel of the thread on her fingertips and the vibrations of the sewing machine on her palms reminded her of her mother, and she wanted to give some of those memories to her child.
But Kimberly couldn't even tell you how to thread a needle anymore. Her grandmother sewed out of necessity. Her mother sewed out of nostalgia. But Kimberly doesn't sew at all because, without necessity, nostalgia rarely makes it to the second generation.
The Christian faith is necessary. You are dead without it and nothing in this world can replace the salvation that Jesus gives to those who hear and believe His Word. But when your pastor doesn't see you for months at a time, when you let every conflict bump the Divine Service off your Sunday schedule, when you never talk theology with your children, you teach them that the Word of God is nothing more than a trinket we pull out of the closet whenever we want to taste the sweetness of our familial heritage. And when you teach that to your children, your children will not grow up to be Christians. They will not believe anymore than Kimberly sews.