When they were slaves, they had complaints. Now, that they are free, they have complaints. In other words, they were human. And humans complain. Listen to talk radio some time for an example of complaining.
Or, come listen to me sometime. Hear me talk about the good old days. Or, I'm guessing, listen to yourself.
The Lord had heard their outcry in Egypt and sent Moses to bring them out of captivity.
But freedom is tougher than they might have anticipated.
This text reminds us that we too are living somewhere between where things were really bad but are not yet perfect.
And as the Lord had heard them in Egypt, the Lord hears them now--and again responds to their complaint.