If I had issue with a UPS or other delivery person I would first try to speak with them in a respectful manner. They have a job to do and not an easy one with the current temps and driving conditions. I would bet they get far more complaints about not delivering because of no one signing than the reverse.
I have delivery guys that will use tractor or skid loader to load or unload freight when no one is around.
My mail carrier leaves mail at one of the neighbors if my lane is snowed in, saves me the trouble of pulling him out.
I'm pretty sure they would be in hot water if their supervisors knew.
Lots of advantages to staying on the good side of delivery people.
As someone else pointed out, treat your waiter like crap and that's what will be in your food.