Threads where this type of thing has come up so the search will help.

That said it may be a simple as recognizing the preponderance of evidence that Dead people tend not to fight back thus throughout history that seems to have been a favorite option.

As Intel indicated though things are somewhat more complicated in societies where death of one's family/Tribe/guest requires a blood for blood action against the offender due to not only cultural but generally historic practice. That and the many other factors such as need to be able to focus on finding bad guys vs having to look everywhere since you never know who might have died let alone who might feel they need to make it right.

Thus "eggshells"