Emulated floppy sound is definitely useful to indicate if a program (e.g. on C64) is really loading such slowly or has crashed in between. It does not matter if it sounds a bit unrealistic. But please do not come in mind to implement this with netlist instead of samples if that will slow down emulation. Diskette drive brands anyway differ in sound (and wobbling floppys even worse), so there can't be one perfect solution.
Almost 2 decades ago I tried to emulate circuitry with relay sound of 2 EM pinball machines in Visual Pinball and even tried hard to mimic some ball rolling noises.http://weltenschule.de/pinball.html
Despite it sounded often unrealistic, it definitely improved the atmosphere of EM pinball games. Nowadays it would make much sense to write an EM pinball emulator that can execute the original wiring schematics as program code, since the schematics of most pinballs are available. (I had planned such things but never continued.) Each relay and mechanical part should have its own distinct sound, which nowadays would perhaps use filters and stereo effects and not only one sample like the relays in my crude code.
I remember the Schneider/Amstrad PC1512 from shopping centers. It had GEM desktop and a strange flimsy mouse plug that looked like a telephone receiver plug (smaller version of ethernet plug). Later I saw that kind of mice only in toy laptops (VTech etc.,with very short cable).