"... but the situations and principles involved seem not all that different."

Exactly... depending on a gun somewhere 'handy', like a bedroom drawer, for 'self-defense' in case of intruders, is FAR more often likely to be useless or lead to such tragedies.
If it happens in the middle of the night, most people are far more likely to be sleepy, confused, and in a hurry... leading to mistakes.