My wife actually noticed the food thing on her first time watching TNG, DS9, VOY, and ENT. I have to give her credit... I've seen every episode of those shows many, many times, but I never noticed that until she pointed it out. (It's one of the reasons why I love rewatching shows with her that she decides to check out... she thinks of things that never occured to me.)
Great example: "SECOND SIGHT", DS9. Sisko and Dax are on the second level of Quark's and Dax asks for something on Sisko's plate that he wasn't going to have but she wants because "it's delicious and I need the calories to keep up with Seyetik." She puts it on her plate, they talk for a minute or so... then she heads out, without
touching what she just took from his plate.
She notices that no one ever bothers to finish their meals, or they get interrupted mid-meal. I was telling her the real world reasons (doing multiple takes of eating not being something many would want to do, etc.), and for STAR TREK, leaving the food is not necessarily wasteful because it's replicated and it would go back in there after they get back to it, anyway. But we also noticed this in other scifi shows, like BABYLON 5, where replicated food is not a thing.
Bottom line: now that she pointed it out, I see it every time in every show or movie I watch, too.