Because C as in Caren and K as in Karyn. Because Bill and Will sound the same, especially if you have an accent. Also because if you just say Alpha foxtrot november, it’s shorter than saying A as in Apple, F as in Frank, N as in Nick etc.
But you do you, I just find it extremely convenient to use it to make it clear to a phone. If you want to stay cute and confusing that’s fine with me.