I don't understand how our democracies have led to so much instutionalized cruelty, what's the goal? Deterrence? Does it make sense to be afraid of a single ind

I don't understand how our democracies have led to so much instutionalized cruelty, what's the goal? Deterrence? Does it make sense to be afraid of a single individual to the point of depriving this person of so much? It's really sad.