I'm a huge electronic music fan (and of much less commercial stuff than my example) so it's not a slight on it at all. The problem isn't the style of music. The problem is that DJ's play recorded music and all recorded music (regardless of genre) is heavily compressed so has much less dynamic range. A live band will be much less compressed so there will be much greater and more frequent variety in volume. If a metal band were to get up and play their CD instead of playing live the same issue would occur.