The actions of Ubuntu affect people using other distributions. If Mir is completed and Nvidia, ATI and Intel decide that they will support it and no longer maintain their X11 drivers, that means that other distributions will suffer because of Ubuntu's actions.
It's like having microsoft control a standard, it's why the guys who develop mono are off their rocker. When you let someone at the wheel who completely hates what you are trying to achieve, he's going to steer things in bad directions. What's worse is that wayland was doing was simple. X11 was an old old standard and wayland was just moving in to replace a crufty piece of open source.
Some people were OK with it, some people weren't, then all of a sudden ubuntu goes and makes a THIRD standard, citing a laundry list of nonsense reasons to abandon all that work. We know the reason they did it, it's the same reason they made that ridiculous unity DE. They want control.
