Because we believe that somewhere in the nest of paradigms contained in the phrase "missional church" lies nothing less that the future viability of Western Christianity.
In short, apostolic movement involves a radical community of disciples, centered on the lordship of Jesus, empowered by the Spirit, built squarely on a fivefold ministry, organized around mission where everyone (not just professionals) is considered an empowered agent, and tends to be decentralized in organizational structure.
Interestingly, it's as though the gospel story of Jesus is the archetypal heroic journey, the embodiment of the very adventure that all people in every epoch have desired.
The appetite for adventure and risk is not exclusive to young Christians. In face, it seems to be a fundamental yearning, knitted into the fabric of the human soul.
When the church is in mission, it is the true church. The church itself is not only a product of that mission but is obligated and destined to extend it by whatever means possible. The mission of God flows directly through every believer and every community of faith that adheres to Jesus. To obstruct this is to block God's purposes in and through his people.
Whether [new Protestant church movements] place their emphasis on new worship styles, expressions of the Holy Spirit’s power, evangelism to seekers, or Bible teaching, these so-called new movements still operate out of the fallacious assumption that the church belongs firmly in the town square, that is, at the heart of Western culture. And if they begin with this mistaken belief about their position in Western society, all their church planting, all their reproduction will simply mirror this misapprehension.
Put simply, the church finds itself in a post-Christendom era, and it had better do some serious reflection or face increasing decline and eventual irrelevance.
The church of Jesus needs to wake up from the exile of passivity and embrace liminality and adventure or continue to remain a religious ghetto for culturally co-opted, fearful, middle-class folk.