Because I like the blend of qualities it offers for what I do and how I use a knife, Tranter. As you point out, knife steels, like gun types and calibers, are always compromises. No one has yet invented a steel that possesses all of the qualities one would like to have in a blade in full measure, all at the same time. The vanadium in the VG-10 allows it to take an edge one could easily shave with, though it will not hold an edge quite as well as certain other, harder steels. Both are excellent alloy steels, though they are somewhat harder than I generally prefer in my blades. The D2, if memory serves me, is often used for files is it not? I have several knives in ATS-34 and they hold an edge quite well. It's getting that edge on the blade in the first place that can be a PITA. Actually, one of my favorite steels is one of the oldest, 1095. It's high-carbon, not a stainless, of course, and softer than most steels used for blades today, but it will take an edge that is finer than anything I've ever encountered. As I recall, that is the steel used in the original Marine K-Bar knives.