As a twenty one year employee in the grocery business and a few years on the reset crew, I have moved items in many of stores.

As stated, there are many reasons to reset a stores layout. Marketing research is a big deal in the grocery industry, and they study YOUR habits closely. Have you noticed that dairy products, milk and eggs are in the rear of the store? 85% of shoppers buy dairy items on each visit. The path from the door to the dairy items takes you down the HIGH Impulse isle, Chips, Soda, or seasonal items and high profit items. They know that every minute they keep you in the store means extra $$ in their tills.
Also, many people do not know that the products manufacture pays the store to get their items at eye level, yours and your kids.

Happy shopping, and don't forget to take a list, those that don't spend more.