Speculation, rumors and hearsay are not the way to hold a debate!
Every carrier I know of who operates straight trucks for LTL DO NOT pay the drivers less, regardless of the class of license. Parcel is NOT the same thing! FedEx Express has several of these trucks and it's my understanding that they are paid more than package car drivers. The same is true of UPS. However, comparing a non-CDL P&D operation to a CDL P&D operation is NOT an apples to apples comparison.
You want business sense? Here's some for you. FedEx Freight buys non-CDL straight trucks and hires someone with ZERO experience operating a vehicle larger than a Toyota Corolla. A month later he gets into a tight residential area or downtown core with his little box truck. Low bridges, low wires, low tree branches, low awnings and overhangs, parked cars and other delivery vans are now facing a driver who has never been trained to check their height. Damaged equipment, damaged freight, and a driver who probably quits because the job isn't worth the trouble because he has no incentive to stay. The theoretically larger and cheaper driver pool starts looking like a bad idea really fast if FedEx now has to invest time training every Tom, Dick and Harry who wants to work a pump truck all day.
And THESE are the guys they're going to send out when freight is light? Stop lying to yourselves. You're assuming people are desperate enough to sling freight for a courier's paycheck, and I say the young generation is lazy and uninterested in working that hard for a paycheck. In my experience, straight truck drivers are the first to be laid off when freight is light because they're easier to replace than increasingly hard to find CDL drivers.
A company like FedEx isn't stupid. Saving a few dollars an hour is not reason to waylay drivers they can't afford to lose. Final Mile Service can't replace a 48' or 53' van, you'd need two of them to replace one CDL class vehicle. And it's cheaper to operate one CDL 48' van on a longer route when times are tight than two box trucks.