As a materials engineer who works for a steel company (although my background is in blast furnaces and iron ore smelting - not micro alloying) maybe I can shed

As a materials engineer who works for a steel company (although my background is in blast furnaces and iron ore smelting - not micro alloying) maybe I can shed some light. It largely comes down to enconomies of scale you can certainly make specialised grades of steel but often times it is not profitable to do so. Steelmaking is like most manufacturing process, cost decreases with scale. Usually the specialised grades simply aren't in high enough demand to recoup the costs involved in producing them. For some grades the techniques to produce them are suitably differnt from standard grades that lines needs to be diverted and retooled to handle them, which impacts on yield and causes losses due to downtime etc. Not to mention many of the specialised alloying elements like Niobium etc. are also stupidly expensive. Buying these in small quanities is probably not ideal and I'd imagine its probably risky to buy in bulk because orders may not be filled quickly and business doesn't tend to like having capital tied up in raw material stockpiles. Competition is also very fierce, for a while there has been an excess of steel capacity largely driven by rapid expansion of China's steelmaking capacity. So there is a lot of pressure on keeping operating costs per tonne low all of this kind of leads companies towards where the biggest returns are, which is producing the high volume steels at lowest cost. Thus most of research effort gets directed here as well. Thats not to say R&D isn't happening into specialised grades, its just not where the big payoffs are currently.