Around here there are three towns in a row that have one; St George (90k), Washington (30k) and Hurricane (20k). The one in the middle borders the other two. The rest of the burbs are under 7.5k, so they have to pick the closest one and go there. The hub of the next county north, Cedar City, is 30k, so it has a Walmart. Mesquite, NV (20k) is the next major town southward; Walmart. Out in the boonies, there is a Walmart in Richfield, UT (8k) and there is one in Page, AZ (7.5k). The next one will probably be Moapa Valley, but they are only at 7k right now, so they don't have one. Even with a Satellite town contributing another 1k, and an Indian Res contributing some more on top of that, they don't get one. They have to leave the northern shores of Lake Mead and either go 30 miles to Mesquite or 40 miles to Las Vegas, if they want to shop at one. All the other towns in that region are smaller than Moapa Valley, so they don't get one even if they are hundreds of miles away from the nearest Walmart, and it doesn't particularly seem to matter if they have a few satellite communities that bump them over the number.
Now I could have expanded my data region in order to include greater Las Vegas, and that would have added a lot more data points, but I don't really have all their suburban boundaries memorized. They don't even really have suburbs in the traditional sense. It is difficult to tell where North Las Vegas ends and Las Vegas begins, for example. Also the Las Vegas strip is not actually in Las Vegas, but it is contained mostly in Paradise, and even spills over a little into some other suburb. You won't see the term "Paradise" anywhere on the strip; at least not as any sort of indication of your geographic location.
If instead of going to Vegas, you turn north on the Great Basin Highway, you will make it across the entire length of the state without ever encountering a town over 7k or a Walmart. Twin Falls Idaho would be the first town that you would came across with those two descriptors.