If those patents hadn't been, or had they been shorter lived, or if antitrust law was more robust, we might have seen a lot more investment in optimizations on and variations of the NiMH chemistry.
I guess part of the reason is that the "M" in "NiMH" stands for Lanthanum - a rare earth element which happens to be used in catalysts facilitating oil refinement.
Of course catalysts are consumed slowly, but you still don't want any disturbances in the supply of a key element.
Which might make a difference or might not, I don't know