They do and with iPhone this line is separated by camera quality. The image signal processor (ISP) in the new A-series chip needs to be more powerful every year to enable even better camera features.Apple seems to be drawing a line between the low product and higher end version with Pro.
But Apple can’t save money by creating two chips with two different ISP's. Instead cheaper iPhone variants are created by the number of camera modules and stabilizers.
The X-variant of a chip exists, only because without so many GPU cores the chip area is actually a bit smaller and the chip therefore cheaper to produce.