Just a thought for my own curiosity, but could it be the lack/reduction of UHF and VHF channel broadcast due to digital TV? If I interpret what I have learned about FM and V/UHF through the years. That, they very close in bandwidth and maybe less pollution of overlapping frequencies allow the tuner access to a cleaner signal, resulting in better sound quality.
Again just a thought not an explanation, no science degree involved.
Again just a thought not an explanation, no science degree involved.