Because cowboys unlike your weird understanding of what a cowboy "is," actually still exist. Some of the people at your local Walmart are literally blue-color workers with the job title "cowboy." Now why you would want those laborers banished to "the shadow realm" is obviously some kind of perverted understanding of class in american society that you need to work out for yourself. Hopefully you can understand that actual cowboys exist to today, but Samurais, since they are dependent on feudalism, cannot and do not exist any longer.