Actually, I learned this when I was studying for a marketing degree back in the day, before I had Matthew and went into law. They move things around so that people will be forced to wander the aisles looking for the things they really want, in the hopes that they will be tempted to buy the things that just catch their eye and they think "oh, that looks intersting" or "I saw a commercial for that, I meant to try it". That's why even established grocery stores will change up the goods in their centre aisles for no apparent reason - they know that their "regular" customers go straight to what they want and don't venture into the other aisles. They weigh the risk between pissing off those who will say "I'm never coming back" and don't, against those who are annoyed but would be too inconvenienced, or will never break established habits, to shop elsewhere.

Ultimately, it's all about the Benjies and who cares about the loyal consumer, right??