It's just very convenient to convert some time-frequency domain to sound, even if frequency is shifted for easier hearing (e.g. how they slow down black hole mergers).

That's because human ear is very good at hearing small changes in frequencies. E.g. first movies vere silent not because they couldn't play the audio, but because they couldn't synchronize between the video and audio.

Human eye is very forgiving to uneven or hickking-up video playback, but not the ear.