Although it is sometimes better not to know than to know, in general, knowledge is power. By acquiring knowledge people equip their brains to make informed decisions about difficult and complicated questions. Informed decisions are the direct result of rational thinking, which encourages the development of logic and reason, which makes people excel at solving problems effectively.
Yes, knowing is almost always better than not knowing. If you are to live in ignorance then you give up the opportunity to determine your own fate. With knowledge comes power and the ability to control your destiny. For example, if someone wanted to remain ignorant about whether or not they have some deadly disease they give up the opportunity of potentially curing themselves if they are diseased.
When you know less, you worry less. Why would people want to worry? That stresses people out! Everyone should be happy and if no one is happy then how is the world suppose to grow and become more intelligent? It's that simple. People don't need to know everything. More intelligent people aren't as happy as the less intelligent.