I'm not talking about extraordinary events like a giant meteor strike though. I strongly suspect there are plenty of buildings that would collapse if there was a small flood or if they were hit by a car in the wrong place when they have been designed to remain standing in those circumstances. They're incorrectly designed, or incorrectly built, or incorrectly maintained. There's so many ways for things to fail. The only reason they've not collapsed is because those circumstances have never arisen. They probably never will. That doesn't make them correct.