Why there are "unnecessary" bricks in 60080 LEGO City Space Port? I previously asked about bricks in invisible places. Now I have second question. There are some bricks that are hardly visible, and in no way contribute to strength of a model. For example lime brick inside space shuttle or red bricks in the launch platform. 

Note, as you can see in instructions step 14 - there is nothing on the other side of red brick. It connects only to the long gray technic brick.

Is there any purpose? Are these bricks there to symbolize something? What's the benefit that would justify cost?
I have always assumed that the pieces in question were place holders to simplify assembly.  Their bright color and location help insure proper alignment for less experienced builders. One must realize that the set is marketed to 6-12 year old's. I imagine their testing has proven that such aides are very useful for younger builders.