
While scales are great for getting your fingers and brain in shape to play single-note solos and melodies, there are situations in which a knowledge of the chords you’re working with is a big advantage. One good example of this is the trio format, where you might only have bass and drums for support.
There is a limit to how much a bass guitar can convey harmonic details (such as a major or minor chord) without forfeiting its main function of keeping a consistent low-end, so it’s down to the guitar in this context to provide more harmonic and melodic content.