The question is not whether you need good olive oil. The question is which good olive oil you need, and what you plan to ask of it. A bottle used to fry onions has a different working day from one brought to the table at the last moment.
Keep a generous, dependable extra-virgin oil near the hob. It should taste good and behave well under everyday heat. For salads, grilled vegetables, and a slice of warm bread, keep something brighter: green, peppery, and full of the place it came from.
The finishing bottle is the one you use sparingly. A spoon over beans, a thread across soup, a last gloss on bitter leaves: this is where a vivid, carefully chosen oil has room to speak. Store every bottle away from heat and direct light, and buy a size you can finish while it is fresh.
Three bottles, three jobs, fewer compromises. Taste them side by side with a piece of bread and a pinch of salt. The best oil is not the most expensive one; it is the one that makes the next bite make sense.
There is a particular pleasure in learning the small differences. The first pour for heat, the second for shine; the right salt at the right moment; a table that waits for everyone to sit down.