I worked as a supervisor for one of the Big 3 NA auto manufacturers. We track a lot of different things for different reasons:
*Each employee has a RFID badge that gets them through the turnstiles - tracks in/out of the plant - are you late? you came in one minute to the bell, while technically you are in the building on time, we know it takes 4 minutes for you to walk to your station, another 3 to get your safety shoes on. you're late. You stayed late 2 hours? This will also help me pay your overtime.
*This badge also tracks which entrance the employee used. Did they come in from the other side of the plant? through the office?
*Same system tracks call ins. Employee calls in sick or late. Is there a pattern in their absenteeism? It also helps you know if you need extra people to run your line or not. Your Required To Run # is usually upped by 2-3 to account for absenteeism, but if the numbers fall short, you need to borrow people from other lines. You're over-roll? Send someone to another line or home for the day.
*Each employee has a computer at their station. This tracks, by VIN, which car is in station at which time and which operator (via employee #) is working there. The operator can identify defects as they happen/notice them. This helps track defects, or retroactively, the source of missed defects. This is important information when it comes to government mandated safety issues and recalls. Jonny is responsible for securing seat belts, his gun reported a torque failure. How did this happen? This gives the supervisor something to investigate. Could be a bad tool setting, could be a missed operation, could be defective parts. Knowing who is on the job helps to get answers. Sally keeps inputting the same defect over and over. Is she doing something wrong? Is she following process? Is this a real but "acceptable" defect? Is she just being a dick? All important questions.
*The lines move on a chain conveyor system. You can see in real time when and where a stop occurs. Get the same stop from the same station repeatedly? This gives the supervisor something to investigate. Could be an operator not following process (SWI), could be a bad tool that is holding up the job cycle, could be that the job is over cycle and cannot be performed in the time given according to the SWI (happens during productivity initiatives), could be a new operator being trained and hasn't learned the process fully yet (also happens during productivity initiatives).
Ultimately, the "tracking" is all about increasing efficiencies. Once an employee is in the building they can move pretty freely without being noticed, unless they have a supervisor who is paying attention. It's important to be on top of when your people are making $34/hr.