Because it is what we learn in school as kids. We are persecuted for saying "I don't know" and here we are. Everybody have opinions on everything. A lot of peop

Because it is what we learn in school as kids. We are persecuted for saying "I don't know" and here we are. Everybody have opinions on everything. A lot of people think, that they know a lot. But actually only few people actually know something.