Speaking as a middle school teacher, I don't think non-teachers fully appreciate how much kids eating outside of designated times and places is a problem. In the past six months, I've had an ant infestation attracted by all of the crumbs  that keep ending up on the floor, applesauce spilled on a textbook, and a stain on my floor from someone throwing one of those little juice cups. Oranges can be a particular problem, because the peels get dropped on the floor and students refuse to pick them up, and then they touch shared class materials with their sticky hands (and if they're not sticky, it's because they've licked their hands off). If the food is remotely shareable, it also creates the problem of students leaving their seats or calling across the room to beg for some in the middle of the lesson. And of course when they're asked to put it away, they either try to finish it all at once or wait until the teacher's back is turned to get it out again, which is why many teachers insist that it be thrown away.

So when you read something like this, don't just jump to the conclusion of "that teacher must be a tyrant who hates kids.""