The overwhelming reason is the sound quality. They sound simply fantastic and are built like audiophile equipment.
Often, high end audio equipment manufacturers choose to implement only the technology that can produce the highest quality sound and is ubiquitous. The connectors they support can get the best sound out of the unit. If dual AES becomes ubiquitous I am sure they will add them.
I always choose a component based on the sound… I leave them to choose the ins and outs. Mid-fi and low end stuff is chosen on the basis of connectors, buttons and knobs.
I own a N100 and W20SE