Why do they use numbers instead of names? Like I get that it is supposed to standardize things and I think signify rank, but it's just a lot to say. Like if you're trying to communicate in battle, it's gonna be really hard to be yelling FN 2189 rather than just STEVE or SERGEANT GREER.
Like anon said, one, to dehumanize them, and two, for easy identification and 'storage' of sorts. You could send it one 'group' like YT 100-200
However, it also proves a fault that there aren't enough (if my math is correct), since there are 676 different letter combinations, and for each of those (assuming it's 000-999) so only 676,000 names are available, and seeing the numbers at which they spend lives, I don't think that's enough.
The Frist Order is similar to Nazi Regime. During the Holocaust they wood give Jewish people numbers. It was a form of psychological torture. Take away the individuals sense of self worth and importance and you get a more obedient person. By not giving the troopers a name it took away the thought of Im a person and can make decisions based on my own personal beliefs and values, instead it made them think there are just another part in the machine and therefore have no choice in what is said or done.
it might be like how clones were given numbers but eventually got individuality through their actions
seeing as FN 2189 was on his first ever mission, and grew up being trained and working sanitation, he obviously didn't have a nickname yet
that, or the empire doesn't care about the stormtroopers like the clones and they are literally just cannon fodder
plus usually the generals have names, and can just command entire squads without needing to care about individual names (i know kylo ren knows Finn's exact number but he is sith so it doesn't count)