Why would louder be better? Right, there is no reason. 16bit sound has a huge dynamic range so that cannot be the reason. Mp3 does not even have a bitdepth so theoretically it can have an even bigger dynamic range.
I understand when you are using dynamic compression for artistic reasons (you really like the sound better).
But using hyper compression, multiband compression, softclipping and whatnot just to get the music louder is a bad reason imho.
With loud mastering you only increase the chance that you are getting clipping or destoying details in your music.
IMHO the only genre which might get away with loud mastering is (hard) rock. But even with that genre the mastering goes over the top nowadays. Listen to Red Hot Chilli Peppers - Californication, Stadium Arcadium or Metallica - Death Magnetic. Do you like that sound? (I don't). The vinyl version of Stadium Arcadium is known to sound better than the CDs due to quieter mastering. Same goes for Death Magnetic and the Guitar Hero version.
All other genres suffer more easily from loud mastering and treated even more carefully.