As much as I'd like to think you could get solid answers to these questions, the truth is that you probably never will.
I'll do my best of sharing my opinions and tiny bit of knowledge.
As best I know, the cost of steel difference is quite small. Blue steel grades are more than white steel grades...AS most expensive, and then down. However, in something the size of a kitchen knife, the cost difference between the cheapest white and the most expensive blue might only be $5 or $10 per knife.....enough to matter, but in the grand scheme of things, it's small potatoes.
So I don't think cost is a driving factor.
I don't prefer AS to white. I like white steel over any blue....it's totally personal though. Also, white is better as certain things, as is blue steel. Additionally, most smiths seem to get used to a particular steel and stick with it. Someone like Takeda has found a steel he likes and sticks with it. Shigefusa does the same...they use that "spicy" Swedish steel for all of their knives. Watanabe will only use blue in his gyuto's.....but he used white and blue for many other knives.
A knife maker once stated that white steel is kind of the....how did he put it?!?! Something like any smith can forge blue steel as it's very simple and white steel to some degree....but white steel takes a lot of skill to forge VERY well. I don't know if it was marketing hype or not....but it's worth thinking about.
Most likely, and this is all opinion, it's just a matter of a knife maker finding something they like and sticking with it. I like AEB-L and 52100 and make nearly all of my knives from those two steels....but I could certainly make knives from other steels. But, it takes research and testing of each to make sure I'm putting out a good knife.
I don't think reactiveness has anything to do with it.
Lots to discuss here....I'll leave it at that for now.