From Brigid at Home on the Range Blog, Things Women Will Never Understand About Men...I laughed out loud...read the whole thing, by all means:
Men are not really adept at shopping as we know it.
I admit it. I shop like a guy. I plan what I need to get, look at some reviews to see which is the best product and pick it. Then I walk into the store in a manner in which Clauswitz would be proud, cleverly avoiding people trying to spray me with cologne so I don't end up in sporting goods smelling like a Hollywood hooker. I see what I need, I grab it, (pillaging is in my blood), I pay for it, usually cash, and I quickly leave the scene of the crime.
So when you just surprise your mate with "honey would you go to the store and get eggs and milk" and he's sent into battle with no time for preparation, bombarded by countless displays that make no ergonomic sense and people shoving food and products at him with "want to try the new Kiwi Persimmon Pop Tart, now with antioxidants", he just wants to escape and as quickly as possible. Which is why he comes home with a case of beer, a bottle of olives and a birch tree.
Hardware and gun stores are different. Send him to one of those for just one small item and he'll come home with a vehicle packed tighter than the Clampetts truck on Beverly Hillbillies.