Wow, too bad for SBF that the posts got so far off track from the OP. I have no idea of how economics is at work with the carts. Perhaps it a non-issue, the real reasons for the carts being as some have stated above: easy time for pioneers, something of a witness to the world without expecting conversions, status-winning for those permitted to man them. Maybe too it is some feeble attempt in the GB's mind to reach out to, or just a give a witness to, all those folks who are not at home when the publishers come around.
In the territory I live in the Witnesses have come around 6 times or more in the past 18 months. They regularly have a cart at the local Walmart too, and I have intentionally tried to strike up a conversation with those manning them, but to no avail. That's what has struck me about those things. Back when I was in, I would have jumped at the chance to grab a potential "Bible study" from someone who would stop by! But no, they don't do that. That strikes me as very strange.
Beth Sarim: "I can't believe that JW's actually count service time by just aimlessly standing there."
Don't you remember putting in plenty of time going from one return visit to another without anyone being home, indeed without any non-JW ever seeing you? Is this so different? At least this way, "you're still giving them a witness, brother", right?