All jobs are productivity jobs. It is the definition of a job. You are paid to accomplish some process. To be productive. Some non-zero skill is always needed.

All jobs are productivity jobs. It is the definition of a job. You are paid to accomplish some process. To be productive. Some non-zero skill is always needed. Cleaning surfaces in a restaurant happens to be fairly low-skill. There is a high supply of humans who can produce the result - a clean restaurant. Thus, the wage commonly paid for this job is (compared to higher-skilled jobs) quite low.