If I’m in transit on airplanes and in airports for 8 hours and I wear a mask for 7 of those hours, the one hour (or probably less) that I take off my mask to eat a meal doesn’t completely negate the good that wearing a mask does for the rest of the time. I’m still reducing my risk (or the risk I pose to others around me) for 88% of my travel time.
There’s a huge difference between sitting at a table by yourself (or even with a family member) and, say, sitting next to a stranger in an airplane. Walking through the restaurant and keeping the mask on so as not to catch or give anything in passing is sensible. Greater distance means lower risk.