Earlier quoted context omitted.
That is where the loading bays are, so they keep the fridges nearby so cold items have less chance to heat up. Plus milk is often stocked from behind, which can only be done where they have the extra space at the back of the store.
I'm not sure that's a compelling reason. Why aren't frozen goods at the back of the store then? And are you sure milk needs to be stocked from behind? Is it at the back of the store because it needs to be stocked from behind - or is it stocked from behind simply because its at the back of the store?
Plus with thing like milk, it is a real pain to push several gallons uphill to put something else in front (ever try to put a milk container back on the sloped shelf? Takes a couple hands and some fidgeting to do it).