The idea of a safe room is that in case of home invasion (for whatever reason) you have a fortified sanctuary that you can retreat to and summon help. It’s not to bunker down and have a shoot out, it is where a smaller, weaker (or unarmed) person can be safe while waiting for reinforcements to arrive. In one sense, it’s so you don’t have to have a shoot out between you and an intruder. In another, if the intruder does break through the room’s defenses, it is pretty cut and dried that it was self-defense — even in states with a duty to retreat statute.