If digital audio was about bits and bits only we wouldn’t have any problem.
We would stay in the digital domain and enjoy all the robustness of it.
Unfortunately audio is not only about bits but about timing as well.
If we transmit digital audio e.g. using SPDIF, the timing of the signal is used to construct the sample rate.
If the clock of the sender is jittery, we have input jitter at the DAC.
Then there is noise e.g. a ripple on the ground plane. If this creeps into the DAC, this might affect the DA conversion.
Digital audio is:
Bits , most of the time not the problem
Timing, a fully analog thing, never perfect by design
Noise, all components can en will generate some noise.
A good DAC of course has it countermeasures like PLLs, ACSR, transformer coupling, etc. etc.
In essence, jitter reduction and noise isolation.