Why would people post audiobooks in low bit rate stereo?

As most audiobooks are read by a single individual with only a short
segment of music at the intro at the begrinning, why are some people
still posting audiobooks in stereo?  64kbps mono will give the same
fidelity as 128 kbps stereo .  As you are using higher compressing to
save bandwidth, why post in stereo comprimising the quality even
further?