You've got your new camera with ETTR mode set up to shoot that way, because some pundit says it's the best way to expose.
You're at the beach, the sun is setting. You've got the 70-200/2.8 mounted, because that's the lens the pundit told you to buy. You're shooting, it's great, you're zooming, you're zooming.. and the camera stops working. WTF.
What just happened? Is the customer happy with their new camera?
The point here is that there is a world of difference between shooting ETTR by hand, and in programming a camera to do it. There are issues that are gonna turn up, which are not trivial to solve, and all the talk about "blah blah blinkies EVF" won't make them go away. This is probably why Internet Pundits are not system architects, and I am. Well, have been, but that's another story.