Makes sense
Mark S must have realized what a long shot it was that Ubuntu / Unity could inroads against Android or iOS in the phone or tablet markets. Without that, what's the point of a unified interface?
I can't speak to Unity's technical underpinnings, but as a desktop user I didn't like it. I tried it, found it wanting, and went back to my preferred Mint / Xfce setup. Personal preference, to be sure; but if it had been popular then Canonical wouldn't have taken it out behind the shed...