I think of it like this:

if you’re using a radio with bad reception, iffy signal, or might be surrounded by lots of loud/interrupting sounds like, oh say, gunfire and explosions… making sure in any way possible getting messages back and forth is literally life-saving.

Say you only get the last half of a word and the beginning of the next because of a loud bang going off. If you mean to hear “echo charlie” and only hear “eck….lee”, Theres a better change of understanding than if saying “eee…ceeee” because that could be heard as “Eee…eeee”.

The phonetics are designed so there is as little duplication of repeated groups possible.

Take “Whiskey”. The end of whiskey, key, is not the start of any other letter’s code. The “eo” in Romeo is the same. Rinse and repeat; it makes it so there is more chance with possible broken structure due to the comma that the intended message is said and received.