One thing I learned when doing my PhD work is that the brain actually uses the very high frequencies that we supposedly can't hear. Of the many "experimental" devices that I've got to play with, one is an Echofone. I know people who have used them to listen to classical pieces with MUCH better ability to immediately play the piece afterwards. It's on my (long) list of things to try once I can get my studio and other stuff completely back out of storage and set up. This device utilizes frequencies in the 100,000Hz range and was originally designed to help people trying to figure out how dolphins and porpoises communicate.
On the other hand, I've also read about experiments that Tesla (et. al.) have done with low and very low frequencies. Most of these proved that they can be very destructive. YMMV.
I think the current trend started due to the Fletcher Munson effect (which I just happen to have a document about right
HERE ). When playing music at lower levels, the human ear loses (not looses Steve

) both high end and low end which is why they added that Loudness button to car stereos. Unfortunately,
stupid kids some people started using it even when they were already listening to the
current trash music at
ridiculous higher volumes and it caught on (probably because it annoys adults).
Another thing I've learned is that, even if a tune sucks, if it has a good beat that people can feel, they can't help but want to move (or try something approaching dancing) to it.