Grocery stores put common items like milk way in the back, in order to have you traverse the whole store and get exposed to as many meters of shelf as possible. They generally also like to change placement of product, to make sure you don't learn the layout and get too efficient at navigating.
Malls try to balance enabling people to find what they are looking for, but also make sure they don't find it too easily so that people can wonder about and be exposed to as many stores as possible.
If you enter the Dubai Mall from the metro, there's a big sign that points to the left and says "Food Court". You'd get to the food court much faster if you turn right.