I think those labels are chosen by the carriers themselves.
I know but wouldn't it be cool if you could name them whatever you wanted kinda ? I know it is not really required. Not sure how easy that would be able to build into iOS though.
A quick search shows there are Apps for jailbroken iPhones in the Cydia store which do this. So, it's certainly possible. Could be it's just something they haven't bothered with. Perhaps an agreement with carriers, some industry standard or even some FCC rule. I couldn't say why.
I don't see anything recent about that program. I doubt it works anymore.