A dream within a dream form is often the minds way of offering a buffer zone of sorts... Allow me to explain.
When very emotional subject matter in our dreams is dealt with, we often wake up. Emotional frustration, anger, fear etc. in effect, hijack our dream to the point that adrenals pump chemicals into our veins and we wake. When a dream within a dream architecture is employed, we are less likely to wake because we realize that are not directly affected. The dreamer knows that he is dreaming and this awareness allows him to continue on and gain insight of the message from the unconscious that is so very important to us.
sailrmc