In 11:4-5 we are told about the Jews complaining that they did not have meat. They say, "מי יאכלנו בשר. זכרנו את הדגה אשר נאכל במצרים" - who will feed us meat? we remember the fish we ate in Egypt for nothing, the gourd, the melons, etc....
Rashi tells us they had plenty of meat available - the Torah told us earlier about the herds of cattle they took with them out of Egypt, but they were simply looking to complain.
They complain about the lack of meat, but then they remember and refer to what they ate in Egypt and there is no mention of meat. They ate fish and vegetables in Egypt. So why are they complaining about the lack of meat now if they never had meat anyway?
The complaint is "Who will feed us meat". Since they left Egypt, the have gotten used to having everything handed to them on a silver platter. They have not had to do anything. Hashem takes care of all their needs. They put forth no effort at all for anything other than serving Hashem.
They got used to having a free ride and that is why they are not willing to use their own animals for meat. Let Hashem give us meat, why should we use up our own!! Not only that, but when people get things for free on a regular basis, they lose the perception of the giver.
If one works for a living and has to buy food from his own money, he is careful not to overspend, and to buy within his budget and this type of food rather than that type of food. But when somebody gets used to having everything covered and he has nothing to worry about and no responsibilities, he wants the best. After all, it is not his money he is spending - it is someone else's. He loses the perception of what is necessary and what is extra.
In Egypt they never ate meat. But in Egypt they had to work for their food. In the desert they were handed everything with no effort on their part, so now they need meat. On someone else's tab it is easy to insist on luxuries.