It is because when people walk by and look at the JW's and the literature, Jehovah is analyzing their hearts and determining if they are worthy of salvation during Armageddon.
So the most powerful person in the universe is reduced to analyzing people exclusively through a crappy literature cart??
What next? Jehovah™ will require any potential convert to Moonwalk wearing one studded glove, then judge them as to worthiness for Everlasting Life™ based on their skill level?