The point is they are giving people a choice. Some people dont like the fact that the Nexus devices dont have removable batteries or SD slots.
Those people now have an alternative without having to load a ROM on the device.
The fact that they have option means RIP to other developers? lol
You can buy a
HTC First now for $1, and get basically a Nexus device if you turn off Facebook Home.
Nexus 4 is already available for half this new one's price, and it isn't as popular as other phones out there.
The demand for pure android isn't that high in the general population. And even among purist, they will still just root w/e they want.