For one thing, anyone over the age of 27 in 1945 had lived through two world wars. So, they would be happy to discover their countries would see more than seventy consecutive years of peace. I believe the European Union has played a large role in ensuring such long-lasting peace.
It seems that Robert Schuman was right to predict that the European Coal and Steel Community would make war both unthinkable and materially impossible. And peace on the European continent has also meant the spread of democracy. When the Treaty of Rome was signed, only 12 of the current EU Member States were democracies. Today all 28 of them are.