[Terabitten]

Caskets are sealed so the bodies wouldn't come out

I respectfully beg to differ. Once they surface, they start bumping into things, etc., and they do frequently come open.

[AnAmericanMother]

I wish it were true that sealed caskets didn't come open.

Probably the high-end steel vaults would not, but your average funeral home casket can and does break open through deterioration in the ground, running into things, etc. The pine boxes are not really a problem because everything rots pretty quickly and they don't pop up to the surface because there's no air pocket inside.