Japan developed their hugely overdone turned-steel technique because the ore they had to work with was so bad: hammering the garbage out was the only way to get the quality of the steel itself into acceptable levels. As a result, Japanese smiths developed something very close to what we'd now call layered steel.

European swordsmiths (think: Toledo) had access to higher-grade ore, and as a result never needed to develop techniques to work around fundamental problems with their source material.