The tempered scale was created so that instruments could play together without sounding out of tune with each other. Bach's "Well Tempered Clavichord" was probably written with this in mind since musical aggregations were getting larger culminating in the Viennese symphonic styles.

Tempered scales are probably not important in music from Asian, African or less urban areas of the world. They are useful for soloists who don't have large musical aggregations with which to contend.

Frank Hamilton