I have manned a cart.
I'm not technically inactive, irregular or ex-jw, either. I'm only mentally out. I'm actually considered in good standing so far as the elders know.
Yes, you place a crap load of literature. People take stuff for free all the time.
But I have yet to have a meaningful conversation with people. 99.9% of the time it's along the lines of, "What religion are you?" "Oh, you're the ones that can't drink coffee or alcohol." "Oh, I thought you were mormon." "Ok, thank you, goodbye."
When I found people at home in the door-to-door ministry, the conversation was usually more meaningful.
The cart system is lazy witnessing that only real function is inflating distribution numbers and hours spent in the ministry.
I will say that now that I realize that the "truth" is all bullsh!t, I'd rather man a cart than go door-to-door any day.
Perhaps that's why insidetheKH likes cart witnessing so much too, although I doubt he'd admit it.