A good question.

From what I've seen, there was no interest in it by manufacturers so they've went silently with Ubuntu Touch route.

As a side note, I'm amazed at how little love by hackers Ubuntu Touch has. It's what we've always wanted - a "full" linux stack on your phone/tablet that's also a desktop. What's there not to love? Do we really need to hate Canonical for integrating Amazon? It's removed by a single command ffs.