Why have it?
Being a believer, the question comes up. Is the Bride of Christ ready for His return to come back and get us?
We are not yet of one mind to follow and serve Christ the way that He taught us. We are having problems excepting other Christians and their beliefs. We look at our ways, and our beliefs, only to see that our's is the only "Truth." This seems to blind us to what other Christian faiths see as their "Truth".
The whole idea of the Gathering is to show that while we are all different, (and we need to be to bring the world to Christ,) we are in fact just like the human body; we connect together with Christ as the head. We all have a part here on this earth.
We have the Gathering for one reason. That we, for a time (just one day) we can join in together to Praise and Worship the Father of us all.