We have a good friend who works as a driver for UPS (~15 years). Right now he's working every day because it's the busy season - but in recent months he's been off as often as he's been on. Not enough work to go around, so he has the option of bumping a junior driver off his route, or going home. Sometimes he bumps, sometimes he doesn't - he has seniority so it is his decision.
Of course right now it's busy season for all carriers - holiday purchases/gifts etc. and they hire extra helpers from now til the end of the year. Once the holidays are over, business drops dramatically.
LTL is a bit different of course. Have you tried Southeastern Freight Lines? They are pretty good IME...
To steer somewhat back on track... I get deliveries via UPS, FedEx, company truck and small independent courier service (Executive at this end, but it goes to another small company at its point of origin and they network with Executive)... never have any real issues, unless the freight isn't packed properly - have had a few broken light bulbs but that was a packing issue. Most shippers who pack light bulbs pack them such that short of running the package over, most abuse won't harm them.
But yeah, any driver leaving cardboard boxes in the rain is just stupid (back to the original post)... the company I used to work for (small independent local company) would have dismissed a driver for that move.
Jenn