Merging two low attendance congregations together will have one effect.
Those that have to travel further than before will not go as often, and those that need constant hassling to be at the meetings will get less attention and attend less often.
Two low attendance congregations will eventually become one low attendance congregation.
Imagine how far some of the congregation will now have to travel in order to reach the edge of the other congregations field service territory!
Imagine how far some, who live on the furthest edge of the territory will now have to travel to get to a kingdom hall, maybe having to drive past where the old hall used to be!
Impoverished, tight-fisted publishers will not be happy.