title: Why Django does not suggest null=True on string based fields?
body: <p>Django official documentation does not suggest using <code>null=True</code> on string based fields.<a href="https://docs.djangoproject.com/en/2.0/ref/models/fields/#django.db.models.Field.null" rel="nofollow noreferrer"> [source]</a></p>
  
  <p>I understand that they don't like to have two different <code>no data</code> value. Because of this, Django suggests only use empty string as <code>no data</code> value. But, Why they didn't choose <code>None</code> over <code>""</code> (empty string)?</p>