The wealthy usually arrange that their servants eat separately, in their own quarters. And not infrequently, their food is of lower quality. The workers may be unhappy about this state of affairs, but they do not complain, since legally there is nothing wrong.
However, when it comes time to be paid, and the worker notices that he has not received his full salary, he may bitterly remark:
"Why is my salary reduced? Perhaps it is because all year long you fed me such fancy food at your table..."
The servant's principle complaint is, of course, about not being paid in full. However, between the lines we hear a secondary complaint: he is also upset about being served food of a lesser quality.
The Israelites were afraid that they would starve in the wilderness. "You had to bring us out to this desert, to kill the entire community by starvation!" (Ex. 16:3). They asked for food so they would not starve - certainly a legitimate request.
However, when they complained about the difficulties of life in the desert, unlike Egypt where "we could sit by pots of meat" - we hear a secondary complaint, that there was no meat in the wilderness.
Therefore, God informed Moses, "I have heard the complaints of the Israelites. Tell them, 'In the afternoon you will eat meat'" (16:12). But where do we find that they complained about meat? It is as the Midrash explains: In your words, you asked for bread. But in your hearts, you asked for meat.
Adapted from Mishlei Yaakov, pp. 321-322