As a child I studied scales in preparation for NYSSMA solo festivals (NY state adjudicated solo festivals). This was not a regular part of my practice routine. I would try to memorize the required scales several months before my audition date, and then omit scales from my practice routine after completing the audition. My purpose for learning scales was to achieve a high grade at NYSSMA.
Later on I began to play saxophone in a band composed of guitars and drums. These groups played in guitar friendly keys (concert E, D and G) which left me in the keys of Db, B or E (on my alto sax). Their only form of music was lead sheets that consisted of the words and chords (no notation), and they only possessed concert versions of these sheets (not transposed for my key). I then realized the true purpose of practicing scales. I needed to become comfortable enough with these difficult key signatures to be able to play freely and uninhibited.
Scales are just one example of the many musical elements that we practice in our pursuit of musical performance. The more we understand about the purpose and application of studying these elements, the more successful our practice becomes. Often this understanding does not occur until we face a performance situation that demands it. Pursuing various performance opportunities and the knowledge of teachers with vast performance experience will help to accelerate our growth in this aspect of musical performance.