People (even experienced engineers) are often fooled by relative volume. If an eq plug or saturation plug boosts the overall RMS by 1 db, you may think it sounds 'better' even if it doesn't. And when toggling back and forth between a crushed master and one that's less crushed, the more crushed one will sound 'better' at first. Of course, if you adjust the volume to match the RMS, the one with more dynamic range will sound better, less fatiguing, more exciting, etc. And most bands understand as soon as you demonstrate. But, they question whether fans will be fooled by the loudness, as do labels, etc.
Of course, no one actually says 'Gee, I love the music, and the songs are great, but it's just not quite as loud as this other, less-great album, so I'm gonna buy the less-great one!'
It's stupidity piled on idiocy. And we wonder why people are perfectly happy to listen to poorly encoded mp3s. They've heard crappy CDs on crappy FM stations for 20 years. There are kids who have never heard a CD or radio station that wasn't over-compressed and limited to hell. They think that's how it's supposed to be!