Every week I have to go to the store to get groceries.  First, I take an inventory of the things in my house and make a list of everything I need to make sure to pick up while I'm out.  I then get into my car and drive across town to the store.  I find a parking spot and get out of the car.  I walk into the store and get a grocery cart.  As I walk into the store, I grab a sale flyer and look at the store's sales and specials.  Next, I start going down the aisles at the store, adding things into my cart that are on my list or are on sale and would be appreciated at my house.  After I am done shopping, I get in line to check out.  I wait patiently for my turn.  When it's finally my turn, I check out and pay for my items.  Lastly, I drive home and put away the things I just purchased from the store. 
Question: Why did they need to go shopping?
they were low on a few items