Many materials are <i>stronger</i> than "steel"[1], and a few of them are quite manufacturable in principle, but nearly all of them suffer from defects in other attributes.<p>Hardness, toughness, resistance to temperature extremes and degradation by environmental chemicals, ductility/workability, cumulative stress resistance, material cost, toxicity, costs and complexity of making joints, repairs, and other workings, and the ability to <i>vary</i> strength, ductility, hardness, toughness, corrosion resistance, and thermal properties: all of these and more matter greatly.<p>"Steel" (as a category of materials) stands out as an all-rounder. Any new material is doomed to a niche, probably a small niche, unless it can exceed steel in all of the above.<p>[1] There is not just one "steel".