The foil pages can be used for this
So although the different surfaces are a side effect of production, consumers can take advantage of the different textures.
The glossy side reflects light and heat more than the mat. So if you want to keep food warm with aluminum foil, you should turn the shiny surface inwards. This way, the heat is better reflected back to the wrapped food.
If, on the other hand, dishes are to be chilled, you should turn the shiny side outwards, as this way less heat can penetrate from the outside inwards. In addition, the matte surface inside the packet can better absorb the heat.