Well, gregorio said some recording have very little stuff above 7 kHz. Doesn't mean even these some recordings STOP at 7 kHz. The stuff above 10 kHz is not as important as people think. 10-20 kHz is just one octave, the highest octave humans can hear (when young). People over 30 years old shouldn't worry about frequencies over 17 kHz AT ALL. It is the 21st century, but human hearing isn't different from what it was in the past. Some things just don't matter. People just assume they do.
At 44.1 kHz spectrums aren't supposed to reach 22 kHz because anti-alias filters aren't infinitely sharp. Spectrums reach, if there is stuff up there, to 20-21 kHz depending on the anti-alias filter and that's enough.
Sorry for the immense delay, just have been busier than usual these two weeks and I want to reply well enough. Okay, so I misunderstood what gregorio stated about 7kHz and took it literally.
I don't want to seem dumb, yet what is an anti-alias filter?