Because .30/06 cases are cheap and plentiful and because good bullets like those made by Speer Inc. in 35 caliber are available, the 35 Whelen still retains considerable popularity.
Due to .30/06 cartridges being inexpensive and readily available, as well as high-quality bullets from manufacturers like Speer Inc. in 35 caliber, the 35 Whelen remains popular.