And you can't really follow Rules 2 & 4 when you holster it, unless you remove your holster first, which is often not a good option (like after the shooting appears to be over, but before others like the police arrive).

I will never willingly carry a striker fired weapon: no external hammer, so if something, like a windbreaker tie or finger catches on the trigger, you can't DTRT with your thumb on the nonexistent hammer to stop it from firing.

Flip side is what one of my instructors called manual safeties: "death levers". If you forget to flick it to safe....

Another side is that manual safeties make guns somewhat "proprietary" as Massad Ayoob puts it. Some police officers have avoided bad outcomes when their weapons were grabbed, as the criminal struggled to make it fire they could take effective action. Not so much of an issue for those who carry concealed.