I think there are more than one reason, but the most scientific one would be:
There is a known truth that a noisy power supply can impact analog electronic components in a manner that can reduce the precision of said components that are meant to be highly precise.
I say this is a known truth, because it is a very common problem amongst scientific and engineering measurement equipment, and it can be traced back to power supplies.
If you hook up an analog electrical component (e.g. dac, amp, speakers) to the Nucleus in any way that the noise from that power supply could interfere with the precision functionality of the connected analog component, then the replacement of that noise source with one less noisy would be considered an improvement to it’s operational fidelity.
I’m not saying that the power supply that ships with Nucleus is impacting any analog components. I’m also not saying that any analog components can be improved by switching power supplies.
There may be some truth in this, depending on how unshielded your analog processes are, or how poor your power supply is.
I wrote a post in as plain of English as I could explaining the difference between linear and switching power supplies here:
In that post, pay attention close attention to how a linear power supply is not always less noisy than a switching power supply. However, old customs and terminology are hard to move away from.
I will also note that an upgraded power supply is often a status symbol, which is another major reason for switching power supplies.
No. I wrote above:
We are no longer chasing after an appropriate partner in this space. If one was to pop up that was enticing enough, we could revisit.