Hi all,
I agree that when a loudness control was properly implemented (some of the old Yamahas had nicely designed variable loudness controls separate from the volume control), it was usefull.
I believe it was dropped because lots of consumers did not understand what it was for. Another reason was that lots of users who had compact speakers thought it "sounded better" with the loudness control on all the time, which would overdrive lower-powered receivers into clipping. The crude loudness controls typically applied 10 dB or more boost in the bass which would make the amplifier deliver ten times as much power.
I recall going to parties in the 1970s where someone with a cheap Pioneer receiver would have the thing blasting a couple of smallish speakers that were obviously distorting because the loudness control was on.
Regards,
