This is something I used to believe. I had simply never given it much thought. Maybe you’re in the same boat?
I made the mistake of confusing headroom with dynamic range.
Put simply, when I looked at the master fader, if there was a lot of room between the loudest peak of my mix and 0 dBFS (clipping, the part where the red light comes on), then I assumed my mix had plenty of dynamic range. I imagined my mastering engineer opening up the mix, smiling to himself and saying, “Man, that Joe has done it again. Look at all this dynamic range!” Wrong.
It turns out I simply had a fundamental misunderstanding of dynamic range. I would hear engineers lament the fact that people were over-compressing their mixes, the so-called “loudness wars.” Everyone was in a craze of adding a big, fat limiter to their mixes to make them super-loud.