Why a "dedicated circuit" when everything gets lumped together upstream of the comnpponent?
Dedicated lines can avoid the noise and voltage drop that may result from daisy chained convenience circuits. It’s a difference you can measure, so it’s silly to debate it.
If an audio user really desires isolation, it might be better to get a hospital grade isolation transformer of sufficient capacity to handle.
Many users do both. It's not an either/or choice.