This is why.
And, this also goes to show that while writing A Memory of Light is a privilege and an opportunity for Brandon, it's also put a lot of stuff on the backburner and that he does still have some contractual obligations to fulfill.
Seriously, I admire his work ethic and also the fairly lengthy disclosure of what's going on and why. I know this level of communication isn't for everyone and that not every author can or should be expected to do so, but it's really cool of him to do so.
Plus, I do like his books. I've got an ARC Warbreaker on my shelf which I want to get to before June.
Oh - and do go find those faux-reviews of The Way of Kings on Amazon. They're a hoot.