Bob Stuart had, and still does have have a choice in the design of his gear and in supporting DSD or not. He rejected DSD for his own technical, sonic and business reasons, hence his gear does not support it. It is not the other way 'round, as you would have it. He is not alone in the engineering and technical community. Many prefer PCM. Others prefer DSD. Anecdote: it is interesting to note that the late, great recording/mastering engineer, Doug Sax, of one-time Sheffield Direct-to-disc analog recording fame, tried DSD, then became a strong advocate of 192k PCM before he died a few years ago.
I try to be open minded, myself. My system supports DSD up to 4x on playback, and also PCM up to 384k. So far, I have yet to hear the compelling sonic difference afforded by DSD. I have also heard other's systems set up specifically for DSD, one at a DSD-advocate recording engineer's home studio, with outstanding components. Again, for me, there is no compelling sonic reason for me to switch to pure DSD playback, given DSD's disadvantages in playback processing, such as the lack of tools for bass management, speaker distance correction and most Room EQ.
...One of the reasons I posted this link: http://www.mojo-audio.com/blog/dsd-vs-pcm-myth-vs-truth/