Why is it imperative to nail down the lid of a coffin?

oh sure, be a pallbearer, trip fall have the corpse fall out and roll on to you, personally i can see that ruining my dayWhy is it imperative to nail down the lid of a coffin?
I don't know about you, but I surely don't want to see a dead body flop out of a coffin. It wouldn't ';gross me out';. Nor would it send me into a ';fit';. Just the same, I don't particularly want to witness such a thing. So, people, please do continue to ';nail down'; the coffin lids.Why is it imperative to nail down the lid of a coffin?
Disgusting people sometimes like to dig up the bodies to see if the people were buried with very nice possessions like...well expensive stuff. Nailing the coffins makes it a tad hard to open.
For those who want to insure they get their inheritance.





Too often they got frustrated when their relatives woke up too soon.
Because the zombies will eat your braaaaiiiiiiiinnnssss
To keep you from crawling out!