I didn't know stainless is a poor sparker steel but it figures since it is non-ferrous metal.
Whoa, stainless steel is not a non-ferrous metal. Non-ferrous means it lacks iron. Things like brass, bronze, Hastalloy, etc... are non-ferrous. Stainless steel is still mostly iron along with at least 11% chrome (usually 13-25%). The chrome reacts with oxygen to form a thin layer of chrome oxide on the surface of the steel. This chrome oxide then protects the iron portion of the steel from rusting.
Stainless steel has more "plasticity" to it than normal carbon steel, meaning it deforms a lot more before shearing. This probably makes it less likely to tear off shards/sparks when hitting it with a flint, but don't quote me on that.
-Blast