Powerchords are neither minor or major and therefore either scale can be used over top of them. Only when a scale is used over them, is a major or minor tonality implied to the listener. The blues scale works very well over these types of progressions being that it contains both the minor and major third in it. A blues scale contains both the Eb of C minor and E of C major. One could also simply play the C major scale over the first 3 chords, and then transition to the C minor scale for the last 3 chords.
Power chords are especially popular among rock and blues music.
The power chord is used a lot by guitar players because the guitar's standard tuning and the distortion's effect upon the sound of the major third. He says it will help me find my way around the fretboard better. It does seem to be helping. Because most music is chord based. If you were able to analyse your pieces at your present state of learning you would probably find that the structures consist of the notes of chords or parts of chords.