Scales matter. Piano teachers are renowned for insisting that this is true, examination boards reward mastery of these patterns, and piano students compare speed and distance as if they are training for field and track. I talked before about why I think scales matter, in my Scales as Propaganda post, and this post follows up a lot of the ideas I put forward there. One of the main ideas in the Scales as Propaganda post is that the reason scales are important is not for technical facility per se (finger strength, fluency, tonal control and so forth) but for a broader (and fundamentally imaginative) ideational and geographical facility with the diatonic patterns that underpin music from the Baroque through to the end of the Romantic period (chromaticisms notwithstanding). What this means in practice is that if you know how to play the major scale in each of its 12 permutations you will have a reasonably high fluency in sight reading
read more Inadequate Indoctrination (or, a practical instance demonstrating why scales matter)