If your hearing loss means that you pick up the sounds from one speaker only, you will only hear the sounds “tailored” to come from that speaker in stereo, so you won’t be getting the full spectrum. In mono, both speakers produce the full spectrum equally, so it doesn’t matter which you hear.

Your question is in the car forum.

I know this talks about headphones, but perhaps its along the same lines?
“I’m not an audio tech, but… For many years, there was no stereo, and one speaker (for a radio, TV, etc.) was enough. Then stereo was developed, which allowed different signals to be fed to left and right channels. This can give clues as to placement; a sound source moving through the recording field would audibly change its position during playback. So, 2-speaker systems became the norm. Coincidentally, we have 2 ears, so headphones (except those terribly annoying ones that get included with speech recognition programs) have 2 sound-generating units. Stereo was easy to implement on headphones, and it made sense! Talking about sounds as we normally experience them in life - We hear slightly different versions of the same sound in either ear, because unless the sound is equidistant from both ears, it reaches one before the other. Subtle reverb/echo cues will also be different if the listening environment is not the same on both sides, due to the presence of reflecting or absorbing surfaces and their distance and orientation. “Mono” in a post-stereo world really implies that the SAME signal is fed to both channels/speakers/ears. There are no locational clues because there is no “separation” in the audio field. If your stereo amplifier/receiver has a mono/stereo switch, toggle it while listening to an orchestra. Suddenly you can’t tell on which side the violinists are sitting, but you still hear them. Both of your speakers are still playing music, but it’s exactly the same waveform, so you lose a sense of position.”

Good luck to you I say. Perhaps you find will help other with hearing impairment.