If you were using Bluetooth audio, or some other source that accepts a digital feed, previously you'd be carrying around two sets of DACs, one of which would be

If you were using Bluetooth audio, or some other source that accepts a digital feed, previously you'd be carrying around two sets of DACs, one of which would be doing nothing but taking up space. Attaching an analog audio cable to a device already dramatically increase it's size; stashing a DAC and ADC in there doesn't make it much bigger. Moving the DAC outside of the device also means you get less analog interference from other noisy stuff inside your device, like radios. The mini PC example isn't quite the same; you always need a power source to actually use the thing. That being said, I could imagine the PS being much smaller if you had access to 12V direct current, like in a car. So it's potentially nice to not require NUC people to carry an internal AC->DC when they don't need it.