When I have to call an airline/booking service, it will tend to be because I need to do something that can't be done online. Unsurprisingly, often this also means that the average agent is not totally clued up on the specifics of what you're asking.
If I need to call Expedia to change dates on my ticket to Jeréz de la Frontera, I don't want to repeat the 4 words 3 times and still have a baffled agent on the end of the line. I'll mention the placename very briefly and quickly move on to say X-ray Romeo Yankee.
Similarly, when calling Korean Air to add a Czech Airlines FFP number to my reservation, I won't wait for them to search the code for CSA.

I couldn't care less if the above makes me sound brash or conceited.

Now, if your only routes are LHR-MEX on BA and AMS-MAD on KLM, I am sure the above won't apply to you.