The life that is in these branches is withering and dying. They cannot produce any blossoms or fruit. It wasn't always that way for them. Each one of us starts out sturdily connected to the strong vine of Jesus Christ. There's better growth that way.
Baptism is the grafting event.
When we are baptized we are grafted onto the rootstock that is Jesus Christ and God's kingdom. It is our job to make sure that graft takes hold and develops so that she can grow and become strong and bear good fruit for God's kingdom. Then as she becomes older, she can keep her own faith alive by seeking the nurture she needs through study and worship and sacraments. You know, many Lutherans have this sick idea that once we are 13 or 14 and have gone through some classes called confirmation, that we don't need any nurture any more. So worship attendance, bible reading, prayer, communion participation and study decrease.