Imagine that they upgrade the touch UI in your car, and it's a complete redesign, but only on one specific screen in a sub-sub-sub-menu which you usually only open while driving.

Now you are speeding with 150km/h down the highway and voila, the screen is gone (it's there in fact, but it's not the same screen any more).

Have fun poking with this new updated UI and workflow.

BTW, this example is exaggerated of course, but not completely unrealistic, and it's easy to find similarly disruptive situations triggered by a UI or workflow change.