Maybe for the same reason why gasoline in U.S. is usually priced in increments of $0.10 as the performance rating goes up (although that seems to be less of a r

Maybe for the same reason why gasoline in U.S. is usually priced in increments of $0.10 as the performance rating goes up (although that seems to be less of a rigid rule lately where I live)? Or maybe for ease of predictability? After all it is much easier to make a binary choice between two numbers with a fixed interval between them, than to choose an intermediate value to the Nth degree.