[jmileham]

As long as there's recorded audio up there, you might as well reproduce it well, and even standard CD-audio goes up beyond 20KHz.

Also there's plenty of individual variance in people's hearing. No need to fit to the lowest common denominator even if the majority can't hear it. As a tall person, I appreciate that airplane seats aren't pitched to cut your kneecaps off after 6'0" (ok, maybe that's generous to the airline industry, but you get the point).