Takeaway
Constraints can come from unusual places.
Do you know how deep a grave is?
Note: by 'we' I mean the United States
It's not 6 feet, but I wouldn't blame you for thinking it.
It's actually 4'11.
Why? Because of OSHA.
If you have a hole 5 feet deep or lower, it requiers shoring (reinforcements).
So graves are just shallow enough to avoid this requirement.
Related: buring a body too deep actually retards decomposition.
Do you know why we started burying bodies 6 feet deep?
It's because of the plague. Specifically, the London plague of 1665.
Burying people shallower than this leads to problems with grave robbers, the local water table, and wildlife digging up graves.