Consider a pure sine wave, it's harder (in theory anyway) to match the signals from the left and right ears, and identify the time delay between the two signals: each cycle of the wave is just like the others, so there's no distinct signature to match and say "the sound reached the left ear 0.5 ms before it reached the right ear". This is especially the case for higher frequencies where there can be something like aliasing.

Animal species sometimes use this in different sounds they make. An alarm call has that kind of "smooth tone" characteristic, so a predator can't locate the source of the sound but it still works to raise the alarm. Meanwhile more social sounds are more "chirpy" and sharp, so they can locate each other.