[1] https://www.amazon.com/Honeywell-Intellisense-FG-1625-Acoust...
(I still think it's insane that the bean counters and value engineers let them include a microphone that wasn't needed.)
Having worked on hardware products, the features planned sometimes (even often!) change after the hardware has been prototyped and an initial production order has been placed. It is cheaper to simply not ship the feature than it is to change the board.
Many in this comment section do not really seem to have much experience with hardware. It is fairly common for products to ship with unused hardware and it much more believable than malicious intent, especially given how disorganized Google is internally.