the tech in the Carver TX-11 FM stereo tuner:
^^^
"In my area, 10 or 12 stations are too noisy for stereo. Pressing the buttons made every one listenable and acceptable!"
The Carver FM tech could (and should) have been used in vehicle FM radios (probably still could be, maybe DSPized).
I had one of those Carvers for many years. The noise reduction eliminated the hiss on weaker FM stereo stations, but it narrowed the stereo image and created a hollow sounding effect with attenuated highs. For its time it was a very creative solution, though. Bob Carver designed some great equipment back then.
These days that sort of thing is all done with a DSP chip in the receivers. I believe some of the modern shark fin antennas on newer cars use some sort of diversity design too.