One character variable names for temp or iterator values are everywhere in programming. But I've never ever encountered one spelled out as a full transcriptions of the NATO phonetic alphabet like alfa, bravo, charlie. Exception is alpha for probability/statistics.
Not all. Military definitely favors NATO, but there are other phonetic alphabets in use. In particular, at least in the US, fire/ems personnel (and sometimes also law enforcement) use alternatives. The one that goes Adam, Boy (or Baker), Charlie, David, Edward, Frank, ... is still widely used.
I've also known agencies to use a mix, like Adam, Baker, Charlie, Delta, ... (a law enforcement agency that I dispatched for back in the 1990's used this version).
Source: was a firefighter and 911 dispatcher in a previous life and still spend a lot of time monitoring fire/ems channels locally just to stay connected to that world.
I don't tend to use single-letter variable names outside of the standard `for(;;)` syntax, but if I did, I don't think I'd replace them in this way.