Well actually I found a lot of restaurants, cafes and food stalls where I saw staff eating behind the counter.. the food gets contaminated and you will notice most don't even wash their hands after eating behind the counter. 

One was neat burger off Regent Street London .. found staff eating behind the counter and I will never go again 

Even the cooks must not eat behind the counters / kitchens. 

The correct procedure for all the staff is to never eat behind the counter or in the kitchen. 

The correct procedure is for all staff who want to eat to get out of the kitchen and counter and eat outside and when resuming duty to wash hands before ..and then cook in the kitchen or serve behind the counter.

Your food can get cross contamination and jutha ( meaning not fresh at all )