We generally treat the boundary between a church and the world outside as a single membrane or condition, and assume that if we make the membrane transparent or easily crossed, if we make a level threshold that can be crossed unnoticed, if we make what's inside the boundary look like what's outside, then people will cross.
But that's still too big a jump for most, all the way from one state to another, all at once. And what if we don't like it and can't get back?
So what if the boundary were complex, had many layers of varying materials, were an entire zone in itself? Supposing all we do as church is actually inside this zone, and the real inside is something else? Supposing church were the intermediate condition rather than the point of arrival?