This may sound like a silly question, but the truth is that lots of churches don't include any kind of formal membership as part of church life. The reasons for this vary.
Some churches see formal membership as too structured, too rigid.
We're all just here to worship Jesus. Just as too much structure can hinder the movement of the Spirit, it can hamstring the congregation. Still others see formal membership as downright un-American. If you've been worshiping at Christ Reformed Church much this summer, you know that formal church membership is part of what we do. During our worship time, we've had new members join by baptism, profession of faith, reaffirmation of faith, and transfer.