Why do the Military, Aviation, and Law Enforcement have...different call signs for the 26 alpha characters?

The use of a phonetic alphabet really doesn't matter what you use (there is a standard one taught by the military), as long as it is clear that you ARE using one. People use it all the time, for instance, spelling their name over the phone. As long as people are aware that you are using a word to represent a single letter, then everything is good.

There is a standard. It's called the "phonetic alphabet". not to be confused with the phonetic alpabet that defines linguistic symbology.

It's commonly used by groups like the International Civil Aviation Organization (ICAO), the International Telecommunication Union (ITU), the International Maritime Organization (IMO), the North Atlantic Treaty Organisation (NATO), the Federal Aviation Administration (FAA), and the American National Standards Institute (ANSI). It is a subset of the much older International Code of Signals (INTERCO).

In it's proper usage, your license plate (1HB D46) would be One Hilo Bravo Delta Four Six. You get a lot of substitutions by people who don't know the correct word to represent the letter or number, therefore you see so many variations.

able baker charlie

to roger fox dog

able baker charlie

to roger fox dog

the chicken is in the henhouse

i repeat the chicken is in the henhouse

marisy dots and dosy dots

my dog has fleas

signed,

your loving son

queen victoria