A honest answer to your question would be because of pride and arrogance. One assembling of believers should suffice. If the Word of God was was not watered down from generation to generation there would be one assembling of believers. A few scriptures:
John 14:6
6Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me.
Colossians 3:15
15Let the peace of Christ rule in your hearts, since as members of ONE body you were called to peace. And be thankful.
Hebrews 10:25
25Not forsaking the assembling of ourselves together, as the manner of some is; but exhorting one another: and so much the more, as ye see the day approaching.
Dying to Christ and living from his teachings, this is as it should be, everything else is trivial to this.
™ Version 4.2
