High frequency extension can give the music sparkle, excitement, momentum, and detail. However, many audio systems:
1) accentuate the upper frequencies to create a coloration of extra detail,
2) have upper frequencies that are distorted, grainey, and harsh due to tweeter/component/cabling deficiencies,
3) lack an upper midrange and a linearity across the frequency spectrum, resulting in your ear perceiving an imbalance.
Some people, instead of trying to address these deficiencies, prefer to reduce the high frequency to produce a more smooth and pleasant sound. It's one way to deal with a very complex problem in audio reproduction.
1) accentuate the upper frequencies to create a coloration of extra detail,
2) have upper frequencies that are distorted, grainey, and harsh due to tweeter/component/cabling deficiencies,
3) lack an upper midrange and a linearity across the frequency spectrum, resulting in your ear perceiving an imbalance.
Some people, instead of trying to address these deficiencies, prefer to reduce the high frequency to produce a more smooth and pleasant sound. It's one way to deal with a very complex problem in audio reproduction.