Cell phone cameras can produce 12-megapixel images, and the data from the sensor is uncompressed. It's very large. Sampling all pixels at once would require muc

Cell phone cameras can produce 12-megapixel images, and the data from the sensor is uncompressed. It's very large. Sampling all pixels at once would require much larger internal memories in the image processors, which would make the chips more expensive and draw more power. Only a few use cases would benefit, so the there's no economic incentive to change how it works.