Because what you hear on a real HDD is the seeks, and the seek time of any SSD is close enough to zero that it probably won't even show up on the HDD LED. All that's left is the data transfer, which are more or less silent on real mechanical HDDs.
That's part of the reason why it was useful to have the HDD LED despite fact you already had the loud HDD. The LED showed data transfer, while the sound indicated seeks.
A nice portfolio art piece for GitHub (could even be useful for keeping an ear on virtual machines)
Come to think of it, maybe the best way is to run the whole system on a VM with a simulated HDD that includes all the delays of a real one, and sound generation. Could also do optical drives.
It makes me wonder if filesystems had recognisable sounds. I feel like I kinda knew what my hard disk was doing just based on the sound.
I also think a large part of the sound was due to the desk it sat on. The only HDDs I run now are in a NAS in a 6 disk RAID. I've had it upstairs and I can hear a thumping sound through the floor downstairs. But now it's on solid ground and all I can hear is the more high-pitched click.