Advancements of herbicides and rising costs of fuel and labor, not to mention the size of the farm acreage, I'm sure make up a lot of the reasons for not running cultivators now. A lot easier to run a Farmall with the narrow tires between the rows than to have a dedicated narrow tractor just for cultivation. Seen several spray rigs in the area running the highways. We don't row crop so I had to do a quick read and it's crazy how advanced they are. 132 foot booms that can be equipped with camera systems that can "see" the weeds and selectively apply herbicide in only the areas needed. Takes a lot of land to pay for one of those.