Big O notation is very important for software engineering interviews. It really shows your capacity to critically think like an engineer. The question that Big O answers is this: “how does the speed of this algorithm SCALE as the input to the system SCALES." That is it. It is a question of scale, not precise numbers. This is why we drop constants. More precisely it is saying that if we give this algorithm VERY LARGE input, what will the UPPER BOUND of the runtime be? What will that tail behaviour be dictated by?