The brake line is typically formed from a single length of tubing. To get the line to route correctly and connect to the distribution block, it needs to be bent into a specific shape. The spiral is a convenient way to incorporate that bend while minimizing stress on the tube itself. A tight radius bend in a straight tube could easily kink or weaken the line, leading to potential failure. The spiral effectively spreads out the bend over a longer distance, reducing stress concentration. Three or four spirals is simply the amount needed to achieve the necessary geometry in that particular area within the constraints of the vehicle's design.
