Bubbles happen because they haven't happened before, people know their history and don't repeat the same bubble. So just because there hasn't been a catastrophi

Bubbles happen because they haven't happened before, people know their history and don't repeat the same bubble. So just because there hasn't been a catastrophic stock market bubble in USA before doesn't mean it can't happen, it has happened in other countries and those stocks didn't recover. Bubbles looks very impressive until they pop, most fall for them, that is why they are bubbles.