I've brought back items that were too large and heavy for me to deal with myself. I've got no problems lifting something heavy if the ergonomics allow for it. However, your 100lb king size headboard set on your 4th story walkup. Nope! Send me with a helper because I'm not taking it myself.
I bring back lots of stuff that management has force upon me. Either the customer couldn't help me, wouldn't help me or weren't home.
For the ones where the customer couldn't help me, a neighbouring route is instructed to help or the customer is asked by the manager to have someone capable of helping be there.
For those who refuse to help, those are left at the station for the customer to pick up. Yes, it's our job but within reason. I'm not tearing my back up because you wanted a gazebo for your backyard but we're dammed if you were going to drive to the store 5 minutes away because you didn't want to have to deal with moving it when you got home. I'll just let the FedEx guy do it.