Imo it’s because of their expectations of how music should sound. They’ve listened to music from mediocre equipment their whole life and enjoyed it that way. Their hearing isn’t used to the subtle nuances and details from a hifi headphone. If you gave your friend the 8xx and he/she spent a couple of months with them then surely they will notice a world of difference.

Another factor is the genre of music you’re listening to and if you are a detail oriented listener.

SHP9500 channel imbalance

The right driver slowly gets quieter until the channel imbalance gets super obvious and then it completely shuts off. Maybe it has to do with the 3.5mm connector as when you move it a bit or you plug it in it affects the imbalance. I tried this with multiple cables, they're not the issue.

Sometimes when I plug in the headphones the right driver doesnt work at all. I've found a few (temporary) fixes: plug the cable in and out until it works, jiggle the cable a bit or shake the headphones. Have you any idea what the issue may be?