I'm sorry, I don't mean to beat a dead horse here but, johnprestor said,
"I suspect they need approval because they're less supervised when they cart witness, and this means that someone could more easily anti-witness or even just advocate some other form of Christianity. Unlike in field service where you're with a group, it's just two of them typically. They're more 'vulnerable' and thus the Elders need to know they can stand up to such pressures."
That makes sense on one hand but on the other it is my understanding and limited experience with jw's coming to my door that they come in 2's and the rest of the group hangs out in the car chatting I suppose? The 2 who knock on the door are in the same 'spiritual' danger as the cart folks. I have even had just 2 come in a car with nobody waiting for them so I could and did take up quite a bit of time with them, long ago. It wasn't pretty, don't ask.
The pressure at the door could certainly be even more so because the householder is on their own turf not a public space. I would think they would feel even more free to be outspoken than in public. It is my opinion that the whole cart 'approval' thing is really just to make r & f feel more 'special' than the rest of the cong. They are so very competent they are 'given' this special privilege. Just more smoke and mirrors on the part of the gb, another way to divert attention to what is really going on in the org. People working harder to get that gold star.