My understanding is pure hearsay, so take that for what it is worth, but it helps to understand western SD. It is big, open country. Where I shot my deer this past fall, the closest "road" was over 5 miles away. And it is more of a driveway, but it is designated by the county. The only way to get there is through "ranch roads", or two track ruts in the pasture.
Additionally, there were issues with outfitters using airplanes to herd deer off of public land and onto private land (Harding County). All that to say, the relationship between SDGFP and landowner/outfitters became very contentious. CO's would travel these ranch roads to verify that clients/hunters were properly licensed. CO's were citing open fields. IMO, it was a pissing match that spun out of control. It was at this time (early 2000's) when the first legislation was introduced to limit the CO's ability to check licenses, i.e., through the Open Fields doctrine. The legislation failed, but in effort to appease landowners, the SDGFP modified its protocols for CO's in the field.