Earlier quoted context omitted.
Beyond that, it may be because Mir is GPLv3 licensed and Wayland is MIT licensed. Just a hunch.
Oh I didn't even know that. That's a great reason to prefer Wayland over Mir or Mir over Wayland. I'm a bit torn now..
Wayland and Mir driver support is pretty much a mystery, and Canonical has been trying to engage hardware designers (Nvidia, Intel, AMD) for support. This recent spate between Canonical and Intel may be indicative that the process isn't going well.
Ubuntu's next LTS release is 14.04 so it's 8 months away, and if there's any surefire way to piss Canonical off then Intel us definitely getting that job done. I'm not trying to defend Canonical but it's hard to ignore the reality of the situation.
I wouldn't be surprised if BSD licensing is on the table front-and-center during negotiations, considering the legal barriers surrounding GPLv3.
Also, it makes me wonder where this leaves Valve. I get the distinct impression that they've been getting cozy with Canonical and they might be getting nervous about the situation.