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.