I imagine many of them have vision so deteriorated that they literally can't see the difference. And I will remind you, these people are still allowed to drive.
This is especially absurd in the context of it already being a restaurant. "How are we going to get pictures for the menu, boss?"
Gee, I dunno. Maybe just make the meal in question and take a fucking picture of it? You are running a restaurant, so I have to charitably assume that somebody there is capable of cooking whatever it is, and plating it up, and sticking it on the cleanest table in the joint for a couple of seconds. For being printed at 72 DPI and the size of a postage stamp anyway, using your cell phone to take the picture will be just fine.