So, the way a commercial dishwasher works is that it fills itself up with 60 liters of water to start with, and uses it repeatedly, with a small amount of turnover, since it rinses with 2 liters of fresh water every cycle, so it drains a little bit each time as well. But, since so much of the water stays in there each time, it gets gross. Part of making detergents is making sure that food doesn't redeposit out of the water onto dishes. Periodically, you change the water for fresh water.
I have heard first hand accounts of places who weren't removing ANY food from the plates before putting them into the machine. So, big chunks of hamburgers and fries were getting sloshed around all over dishes cycle after cycle.
What prompted my comment today was hearing someone talk about a place they were earlier this week where they were changing the water in the machine weekly, at best. WEEKLY. So my brain combined the two, and realized that my dishes could be getting washed with water full of week old hamburgers
Really, it's hot enough to kill germs anyway. But it's still gross gross gross.
Makes me only want to eat at nicer restaurants that inherently care more what is happening in the kitchen, or places that serve me on plastic plates.