The dystopian world in which Gathering Blue is set is certainly no place for children. It's not much of a place for adults, either, but it's much much worse for the kids. This is a society in which only the strong survive, irrespective of age. If you have the misfortune to be born with a serious illness or disability, then that's just too bad. You get taken out to the Field of the Living, where you're left to die. In this bleak, savage world, everyone is pitted against each other in a daily fight for survival, even family members.
Environment is everything here in terms of character development. In this society, those who grow up in a brutal environment are also brutal. Children come to be seen as a burden, a source of unnecessary expense. In all too many cases, it's simply not in their parents' interests to raise them properly. Giving them a loving home and proper food is just a waste of scarce resources. So the children, like Matt from the Fen, are allowed to run wild: filthy, hungry, and in rags.