How much it matters really depends where you shop. Places like Grocery Outlet, or places that don't have super frequent business like small rural grocery stores, can be selling food that _right up to_ the best-by date.
The mom & pop Asian grocery in my hood has a discount section where basically everything is past the best by date. It's all packaged cookies and spice mixes and the kind of thing that won't kill you if it "expired" a week ago though.
