The "fool" is nowhere near your route. He's not even in the US. The layer of the scam you don't know about is that the people who are preparing the envelopes are victims themselves. They just don't know it yet.
Ever meet someone down on their luck, looking for "work from home" oportunities? It won't take them long to find or be found by the "fools" behind the big scam. They'll convince these people that companies around the country are outsourcing accounting work to people who work from home. Sometimes the fools will ship piles of already printed checks for the work-from-home person to seperate, stuff, and mate with the correct address label. Sometimes they provide blank check stock, and a list of people that the checks should be made out to. Sometimes they provide ASD's. Sometimes they provide a newly created fraudulant Worldship account to use.
The work from home victim doesn't know they've been scammed until their paycheck bounces. Often times they've paid for ink for their printer, and maybe even paid the scammers an application fee, or some other kind of fee to get the job. Perhaps they were told it was to bond them, or otherwise insure they are on the up-and-up. (Ironic, isn't that.)
Typically they're instructed to not drop too many envelopes at the same drop box as that can too quickly raise suspicions. They can usually get a month of work out of someone if their drop patterns are diverse enough. It can go on right up to the point that the paycheck bounces. If they get lazy, and drop them all in one box, in a series of boxes picked-up by the same driver, the scam letters (checks) may get intercepted, but it still may continue until that paycheck bounces if no one has the time to catch whoever it is that's dropping the letters.
The biggest mistake that the work-from-home person can make (from the scammer's perspective) is to start dropping them off at a The UPS Store that has a security camera, and suspicious employees who'll get a license plate number. This may actually be the best thing for the work-from-home victim. If the police come knocking on their door before they get that paycheck, before they deposit that paycheck, and before they start spending the money that will eventually come back out of their bank account when the check bounces, it can save them a lot of pain.
Meanwhile, the scammers are sitting comfortably in another country (Nigeria, for example), and they'll just find another work-from-home vicitim. New ones come along each day. The scammers aren't tracking the letters. They just know that a couple weeks after they send out the fake paycheck, they can stop sending more work to that vicitm. If the envelopes are being intercepted sooner, well, no big deal to them, either. Just another cost of doing "business".
