"
It's true that 16 bit linear PCM audio does not quite cover the entire theoretical dynamic range of the human ear in ideal conditions. Also, there are (and always will be) reasons to use more than 16 bits in recording and production.
None of that is relevant to playback; here 24 bit audio is as useless as 192kHz sampling. The good news is that at least 24 bit depth doesn't harm fidelity. It just doesn't help, and also wastes space.
"
24-bit audio is obviously a noticeable improvement even on $150 headphones. I don't know why you think that. Similarly, 4k Blu-ray is obviously vastly superior to crappy compressed streams from Netflix or YouTube.