Subject: Why does the Electrical Field Strength differ between sheets and surfaces

I am studying Gauss's law in my physics class. There are a few concepts that 
arise out it that I need help understanding.

Using the derivation method provided by his formula, we get different electric 
field formulas for the a charged sheet and a charged wall, as I have shown 
below:

    Sheet of Charge, where the E field comes out of both sides of the sheet
              E = (Charge Density/Area)/(2*Permitivitty Constant)

   Wall Surface, where the E field comes out of only the surface that has the  
charge aligned all across it
              E = (Charge Density per Area)/(Permitivvity Constant)

Now, I know that the reason that the 2 exists in the sheet formula is because 
the electric field passes out of two surfaces, front and back. But is there a 
scientific reason as to why an electric field would decrease by half if it 
passes out two surfaces? (I am assuming that if the charge density was the 
same for both a sheet and a wall, the electric field strength out of one side 
of the sheet would still only be half-strength of the electric field coming 
out of the charged wall.) 

Re: Why does the Electrical Field Strength differ between sheets and surfaces