Two reasons for this:
1. More and more people are listening to music through equipment that is significantly inferior. Mobile phones, cheap Bluetooth speakers, cheap earphones - they're all subpar in their ability to render sound faithfully.
2. There is a constant "war for loudness". Once you've listened to a David Guetta song that can be ferociously loud, anything not as loud will be perceived as "soft" that "kills the vibe".