In the U.S., people like to buy in bulk. It's economically logical: if buying slightly bigger version of a product today is going to be cheaper in the long run than buying two of the smaller versions, Americans will commonly bite the bullet and pay that little bit of extra cash today to get the long-term savings. Places like Costco exist, and are generally packed to the gills with shoppers.
The concept of a Costco, and the sheer volume of things people will buy at one time there, would literally blow the minds of small-town Peruvians. Here, buying in bulk is a nonexistent practice, and families instead tend to buy things in the smallest quantity possible. For example: rather than buying a box of tea bags, people will buy five individual tea bags (yes, stores sell tea by the individual bag). Rather than buying a box of soap bars, people will buy only one bar at a time. Shoppers will choose to buy the mini-size version of nail-polish remover (below), rather than the cheaper-by-the-ounce bigger bottle.
This is one cultural norm I still struggle to internalize. I grew up in a household where there are always at least two cartons of milk in the fridge, a Costco-pack of toilet paper stashed in the bathroom cupboards, and more extra batteries in the laundry room drawer than we will likely go through in two years. Before coming to Peru, I didn't question the logic of all these extras, since it seemed very practical to always have one more of an item on hand for when the one in use ran out. The fact that things are consistently on the verge of running out in my Peruvian house continues to stress me out: when cooking lunch, I eye the five remaining matches in the matchbox, and the nagging worry starts in the back of my mind that when I go to make tea for dinner there will be no matches left. Even highly necessary items, like toilet paper or gas for the stove, have on multiple occasions turned out to be gone at moments of need.
However, I seem to be the only one bothered by these chronic shortages. When my host mom discovers that there is no more of whatever product, she simply says, "¡ay, falta ___!" (___ is missing!) and runs down to the corner store to buy some more. This is normal behavior here - I am the strange one for wanting to make sure I always have enough of something. I think this difference in standard house-stocking procedure exists for a few reasons. Peruvians buy based on need - particularly people living on more limited economic resources - and are only going to spend today on what they need today. Planning for the future and putting away savings are also less common practices here, not something that is culturally ingrained that everyone should do. Running out of something is perfectly okay; that just tells you it's time to go buy another round! And even though it might give me a stress ulcer, I can at the same time understand that logic too.