There are many applications developed from linefollowing robots. Redrawing the track lines can be used to in some robot contests. However, an industrial application should be like following:
Do you know the ship board? On the floor of the ship, which is made of steel, metal, is so slippery and hard to walk. Therefore, they have to solder some metal knobs on the floor. The knobs should be soldered alternatively each 20cm - 30cm square. To do so, they dip a long thread into paint, and stretch it from this side to another side of the floor, then flip it. The paint on the thread will draw a straight line on the floor.
With a camera, instead of IR or red light, the robot will track the white paint line to solder the knobs onto board. This kind of robot was built and sold to SAMSUNG shipyard company in Korea.
Building line following robot is the basic step for higher applications, you will learn many things from that. Good luck on your project.