I think we're seeing alot more 154CM because it's made here and the US. If you want to advertize "Made in the U.S.A." there are laws on the percentages of foriegn made materials allowed in your product. I understand that is why Buck went from ATS-34 to the 154CM.
All of my ATS-34 knives say made in the U.S. When I took a tour of the Buck factory the man giving the tour said all there steel was made in the U.S. I was also told the reason for going to 154CM is for better Corrosion resistance.