I wonder if the previous poster is actually referring to a perceptual issue around latency — because the video latency is perceptibly greater than a face-to-face conversation, we may perceive unpleasantness in the audio as well, even though a phone call or audio-only Internet call are generally acceptable.
Now, I'm not sure what video chat tool you're referring to, but POTS audio is awful, even the more modern stuff available for cell-to-cell isn't great unless you happen to have VoLTE - any halfway decent mic and modern audio codec will be much better.