I have a question that's been bugging me lately: why do we avoid the 6th string (low E) when playing a C major chord? I know it makes sense to start the chord with the note for which the chord is named, in this case the C on the 5th string, but an E is one of the notes in a C major chord, so why would it be bad for me to strum the low E when making a C chord? It still sounds okay and I think it makes the chord sound fuller. Can someone explain why it's bad for me to include it? I've noticed this for a few other chords as well, like why not use an open 5th string (A) when playing a D major chord?