Let's say you have to go shopping, and let's create a list of basic essentials you might want to purchase:
breadIn my local grocery store, the bread is on the far left, and the milk all the way in the back. The juice is in the far right in back, the apples are along the right wall, and the toilet paper is somewhere in the middle of the store in aisle 14 or something like that.
In order to get all of the items on my very simple list, I have to pass through almost the entire store -- forcing me past row after row of other items that I probably would never buy if not for the famed "impulse buy" factor. If grocery stores really wanted to make things easy for their customers, they'd put the necessary items up front near the checkout lanes, so I could really get in and out quickly; instead, they have me walking past sugary snacks and soda and frozen goods... walking past everything else in the store on my trek to gather just five items.
Not that I expect them to do otherwise; everyone's gotta make a buck, and this is the best way to make sure people see all that great stuff they don't need, but will probably buy if it's put within arm's reach.