It would be a really unusually venomous postal worker that would mishandle a package because they don't like the patron. That would take extra effort that they just won't expend. Usually all the mishandling and abuse has been done long before your local office ever gets it. Worked there for years in just about every capacity from letter carrier to supervisor to mail processor at the plant. I think normally the problem is that the machines they use to sort packages, by design, drop them a number of feet. Then you've got manual package sorting setups where guys stand in a forest of laundry hampers and throw them into the right containers like basketball stars. They aren't purposefully mishandling, thats both the way things are set up plus they're in a hurry. They'll actually get into trouble if they slow down and pay more attention.
It helps me when my own mailed hatches are 0% to 50% to know these things but that doesn't mean I like it. Some facilities are just a lot harder on things than others. Yeah, I'm one of the unlucky ones too. Not on these eggs, I didn't get any, but I mean in shipped eggs in general.