I work for UPS, I load the brown trucks for delivery. Sure things slip up but you got to consider the volume going through UPS. I handle about 1,000 packages into my trucks alone each day. I have to send damaged stuff to be inspected/repacked etc. Id guess 2 in 10,000 of my boxs dont go out the day they are supposed to because I pass on loading them for whatever reason.
You also get the human factor, people screw up. The packages get loaded on the wrong trailer/truck sometimes and can costs days waiting. If I screw up and load your box on the wrong truck and my driver doesnt want to drive out of his way, your screwed. Some people could care less just like any other job, they dont think of the customer. I kill myself to make sure all my boxs are in the correct truck and ready to deliver. Still mistakes are made and it shows up as you waiting which sucks.
Some drivers are seriously picky about damaged boxs. If theres a bent corner they refuse to touch it. Of course thats 1 less box for them to touch that day so they are happy to refuse. My theory, would you rather have the package today beaten up(no sign of content damage). Or, would you rather wait 1-2 days while its repacked then sent back out. A box can take a serious beating and the stuff inside be just fine. You cant expect a box to make it thought any shipping system and be perfectly fine every time.
Not to rant but it sucks to see 100s of people kill themselfs to move these packages every night and noone cares lol. One of the best things you can do if your willing, is pick up your own package at the center. Call the number and have it held for you. That saves the package from moving across alot of belts and through alot of hands. Sucks having to go get it but keeps you from waiting for the dam driver to show up.