bass note on a C chord

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?

Hi Gary-

We meet again!

You are absolutely right, the note "E" does belong in the C chord, so it would not be a 100% wrong to include it when you strum the C chord.

However, using the low C note (the root note of the chord) as the lowest-sounding note in the mix when you strum the chord gives the chord a kind of sonic stability. In essence, it announces the "C-ness" of the C chord as the most important ingredient in the chord. It gives the chord the most stable, rooted sound.

The same holds true for your other example, the bass note of the D chord. Yes, "A" could be used, would not be "wrong", but makes the chord sound a bit more disorganized.

Does this make any sense?
-Lisa