It's the larger dynamic range. This started(or at least when I began noticing) back when DVDs were created. More space on the disc meant less compression for the contents. Less compression in audio generally results in a larger dynamic range especially when you're dealing with the sounds of explosions vs a human whispering. I remember first noticing this when watching The Matrix when it came out on DVD. Even with a 5.1 setup, you still have to crank it until the dialogue is clear, and then brace for everything else being loud AF.