Child actors are too expensive and tricky to manage, especially re. the volumes required. Each kid will need a parent/guardian on the set etc.
Not practical.
That is fine and well, but gives us the false impression that there will be no child zombies in the apocalypse. That will be the only time you can stab a kid in the face and have people applaud you. HOW CAN THEY TAKE THAT AWAY FROM US?
