Well if all children under 12 were tagged, the "creeps" know if they "take" a child, that child could be easily tracked.
So if a parent "noticed" that her child was missing, she could immediately phone the Police and say my child is missing, give the information, and they will know the location of the child, trace the location and hopefully "rescue" the child before any "serious" harm comes to them.
Belgium has such a 'black" eye when it comes to child porn and abuse investigation and the "cover up" of such cases........