Mozilla's resources are going to mobile. They don't want to be caught dead if the dominant platform really does changes from desktop to mobile. So it's all about the Firefox browser for phone, and FirefoxOS.
All this groaning about them spending resources on UI misses the point. You're just complaining about what you see! The real $ is not going to UI it's going to mobile, and to technical parity with Chrome.
Wonder if they feel the same way about Email - that it's dated technology! Some of the technical issues they left hanging when they took away all the paid developers are significant.