All players, regardless of style, need a working, practical chord vocabulary for playing even the simplest of songs. You can't consider yourself a complete player without a basic knowledge of these voicings.
Blues forms the basis for most successful contemporary music, regardless of the style.
Scales are often over-rated by teachers and players, but a basic knowledge of the most important scale in contemporary music is a must for any decent guitarist or bassist. Knowledge of the notes on the fingerboard continues to elude many players, even those with several years of lessons and experience. Guitarists and bassists tend to be very weak in the area of reading standard notation, a weakness completely unacceptable with just about any other musical instrument. Very few guitarists and bassists are skilled in the area of understanding phrasing, timing, and syncopation, though mastery of this skill will succeed in opening many doors for the aspiring player and songwriter. Most guitarists only view chords as visual shapes, with very little understanding of how they are built, and which tones are in each.