There are so many possible directions to go. One way: it may be that part of the larger story is about levels of learning.

In a previous instance when people complain God responds with care and compassion, quail and easing the burdens of leadership (Nu 11). Like mice in a maze we quickly learn where the reward is and are adept at returning to where it was previously found. So the people complain expecting a response similar to the previous one. This is rote learning, full of conditioned responses, and to be sure, much of our lives are guided by just these types of interactions. Our “buttons” are pretty easy for folk to discover and we are quick to learn theirs, and once they’re hit it’s usually a done deal. So the play is made, complaints are registered; the ball is in God’s court and the people wait to be appeased.

But God has a wider repertoire of response. God’s button will not be pushed, and so we are pressed to learn more deeply about how a relationship can be more genuine, real, authentic. To this occurrence of complaining that is prompted by impatience rather than genuine need God gives them something to truly complain about. (NB: Not that this is done in anger or with the attitude of an abusive parent. It's about learning and the flexibility of God's responses and the risks God is willing to take to move us forward.)

We are pressed to deeper learning by this odd juxtaposition where the source of the ailment turns out to be its cure. And we’re well beyond something that can be grasped by rote learning now.

Have you ever realized, perhaps after years of focus and attention on it, that what you thought you wanted isn’t what you really wanted?...what’s more, that the very experiences that were the most undesirable, most painful are full of the deepest meanings?

(from www.goodpreacher.com/blog/)