Listen to Soma-FM: SF 10-33 sometime. The dialogue protocol between dispatch and police/fire is remarkably controlled and consistent under the most difficult of circumstances.
Exceptions are suspect gunfire, multi-story "working" fires, and foot chases.
Hearing an officer 10-97 (arrive on scene) at a multi-vehicle accident calmly request multiple 408's (ambulances) code 3 (emergency response) belies the chaos at the scene and the intensity of what s/he is actually experiencing.
In SF, with all the hills and low spots, it seems to me the coded dialogue might be more efficient or perhaps easier to communicate. Officers are often 10-1 (receiving/sending poorly) and requested to 10-9 (repeat last message) as in "One Edward Fifteen you are very 10-1. Please 10-9."
And it's weird how your brain picks up on the code and immediately understands the seriousness of the situation. When a 408 is upgraded to code 3, enroute, you sense the urgency. A simple "affirm, upgrading to code 3" tells the officers at the scene that the 408 "gets it" and "hang on, we're hurrying." Usually with the sound of sirens and air horns in the background.
It's not easier or more efficient (it's actually more error prone, since there's less context). The systems also tend to be very regional (a "10-50" can be very different things depending on where you are). Generally the reason its used is "that's how we've always done it". The other reason is that it sounds cooler...
(I work in a system that has (mostly) phased out codes in favor of plain words)
I've heard officers shroud context using codes. "Put me on it, I've dealt with him before. He's a known 800 (mentally ill person)." Or "show me 97 (on scene), subject appears extremely 811 (intoxicated). I'll advise."
Generally we use meaningful acronyms in those cases. Still a code, but one that is a lot less arbitrary. e.g. EDP="Emotionally disturbed person", or EtOH=Ethanol
Exceptions are suspect gunfire, multi-story "working" fires, and foot chases.
Hearing an officer 10-97 (arrive on scene) at a multi-vehicle accident calmly request multiple 408's (ambulances) code 3 (emergency response) belies the chaos at the scene and the intensity of what s/he is actually experiencing.