The way people buy phones is a lot more complicated. Most people pick a carrier first, and then the phone; and most people buy their phone from their carrier store (or a carrier booth at a place like Costco). Thus the consumer choices are controlled by the carrier. If a carrier doesn't want to sell a Pixel phone, then few will be sold, regardless of what consumers might 'want'.
Apple is obviously an exception to this due to their own advertising and stores.
