This is a Bone of Contention between my husband and I. When I go grocery shopping, I buy as much as I can possibly afford, in large quantities, as it not only saves on gas for future store runs, but I will have things in the house to cook with.
My husband goes to the grocery store every day sometimes 2 or 3 times a day, buys small quantities of a few things. He may be on his way to buy, say, ground beef and tomato sauce, and I'll say, "We need aluminum foil and a container of soy milk and a 10 lb bag of unbleached flour, too." He'll say, "I was just going to buy what I'm making for dinner." WTF? You're AT the store! Why should I have to get my car out, make a separate trip, waste gas to buy things we need because you only planned to buy 2 or 3 things, only to go back tomorrow?
Drives me crazy. He also buys the smallest quantity of whatever he's buying. A single roll of toilet paper (or a four pack, and we have two bathroom and go through at least 2 rolls a day in our family) two gallons of water, when we easily go through 3 or 4 a day (I buy water in bulk when it's on sale, like 10 or 12 gallons) or the smallest box of whatever he buys. It appears he's "saving money" but in the long run he's watching the pennies and the dollars are flying out the window.
Drive me crazy, that man.