Labour market determines an individual's worth because it is what provides your income. Also, if you are an assembly worker, you only work on specific skills related to that job. In the case of an assembly worker, you focus on skills such as attention to detail, hand-eye coordination, and so on. Since you're practicing these skills 8 hours/day, these will reflect on your life outside work. Also, there are skill you don't prioritize in work and therefore lose out on these skills outside of your work.