To make it easier for you to hear your music on crappy stereo players, the record industry has been continuously increasing the volume of the songs you purchase. Companies that play back all this loud music often need to get an acoustic assessment report to make sure they are not producing too much noise pollution.
Thank goodness, at least now I can hear all those low beats, right? WRONG, well technically right, but you lose the high beats. As anyone who has ever worked in video editing, sound editing, or anything else weird A/V (audio/video) geeks do on their spare time will tell you, as you increase the sound of a whole song all the medium sound level beats become high beats and the high beats stay as high beats. In effect, this diminishes the quality of the song as the original song was recorded.
The following video demonstrates what the record labels have been doing for years: