Because the demand hasn't been there. If more people learn the benefits of these sensors and decide they want more of them they'll pay more for models that inc

Because the demand hasn't been there. If more people learn the benefits of these sensors and decide they want more of them they'll pay more for models that include them and manufacturers will respond to demand. If people don't know about them, or don't perceive any particular benefit, those sensors will remain niche and expensive.