Parents may teach this to kids but the kids usually notice their parents don't practice what they preach. So they don't either.

The world is filled with people following everybody else off a cliff. If you're warning people or even just not playing along in a time of great hysteria, people at best ignore your warnings and direct verbal abuse at you. At worst, you can face active persecution for being right when the crowd has gone insane. So most people are cowards who go along to get along.