Missions in Church

I feel that a lot of times we think that missions in a church setting are only for those who are already part of the church. For some reason it has become looked down upon for visitors and seekers to join in...WHY?

This generation born from 1980s til now see the great desire for justice in the world. They know that we are all to play a part in redeeming the world...they just might not know that is what it is.

WHY can we not invite them to join us in missions; the churches way of redeeming the world? WHY can't mission be the main focus of the church?

WHY are we scared to invite others to join us in serving?
WHAT do we fear will happen?
WHAT if this is what the church is supposed to do: Figure out where God is working in the world, join in, and invited others along too?