I spent the holidays with someone who does all their searches using only voice input. His eyesight is poor and he chooses to just say what he wants instead of putting on his reading glasses and typing it out. The types of things he was saying and the level of understanding his phone had if him wouldn't have been possible in 2014.
Ironically, I specifically remember the introduction of voice search coinciding with a marked drop in search quality. This had also happened earlier with their "instant results" experiment.
