Deep Blues: Quartal Blues
The answer to me is simple: It’s yet another way to be improvisational with your harmonic vocabulary. These voicings are what you might call “open” sounding, meaning they don’t clearly say minor, major, or dominant. They also sit nicely on top of major, minor, and dominant chords. I also think of them as more melodic harmony. You’re less likely to play one voicing in one place for any length of time—you’ll feel the urge to move quartal voicings around.