The Phonetic Alphabet is used by the military as a way to share letters over audio communication without confusion.
Why Learn? So you don't look like a complete moron improvising your own "phonetic alphabet" in front of people who actually know the real thing. (Speaking from personal experience. - Chris)
It's embarrassing when you make up your own phonetics and get busted by someone who actually knows them. So we recommend committing these to memory...for your own sake!
"Now it's possible while communicating a name or address to someone on the phone, you can use the phonetic alphabet. Being Australian, my accent was very strong when I first came to the USA and this alphabet helped me out with people that could ot undferstand me. So next time you're trying to spell something over the phone, try this alphabet. I'm sure it will help you out." - Advice from Patrick Donaldson - Australian Native, Current Male Military Spouse