Is it normal/common to pay “cooks commission” at restaurants?

I recently visited Seattle with my wife and we had lunch at this restaurant near the airport, nothing fancy, it was an average place, but I was surprised when I got the bill and I noticed that a 5% cooks commission was added to my bill. This was new to me, I’ve never seen anything like that before. Is this common in Seattle?

I don’t get it, the basic concept of a restaurant is to pay someone else to cook for you, why would you add an extra commission on top of the price? That doesn’t make any sense to me, it’s redundant.