You can’t compare firefighters to cops. Firefighters do put their lives in danger all the time, but that’s protecting people from fire. The danger is the fire, not the people inside. Similarly cops are trying to protect innocent people, however they are protecting innocent people from criminals, not necessarily the criminals themselves. It’s not an apt comparison.
Secondly let’s say you pull me over and run my ID only to find out I have a history of unlawful carrying of a firearm and assault. Then you approach my car and ask me to step out simply to ensure your safety more thoroughly. You haven’t arrested me for anything yet, It’s just safer for you to have me outside of my car in case I have a gun in there. Now, what if I refuse? What if I’m extremely argumentative or non-compliant to a lawful order? You would be on edge, right? Now let’s say I’m pissed at you and want to record this with my cell phone which is between my legs in my seat. Your immediate reaction should be extreme caution because I could absolutely be going for a gun.
The fact of the matter is that in this situation I may or may not have a gun, but if you wait until you see me pull a gun out from underneath the seat you most likely won’t have time to react in order to protect yourself since I already have the draw on you.