I worked at two McDonalds, both in the Seattle area, 20+ years ago. The first one was in Mill Creek (a rich area south of Everett), the cops weren't allowed to take discounts. The second place was in downtown (3rd and Pine); we literally couldn't stay open without hiring an off duty officer. Hiring went through the SPD and was tightly regulated.

Offering a cop discounted food to hang out at your restaurant means, while taxpayers are flipping the bill, somewhere else isn't being covered as well. Hiring an off duty cop for part time security work, in contrast, doesn't reduce coverage.