Why are people so set on their opinions?

Everyday I talk with at least one person that is extremely opinionated. It is the most annoying thing when you want to put your own viewpoint in and can't because you know that if you do it won't even be recognized. I know quite a few people that are like this and it's almost impossible to have a conversation with them on the topic because it won't ever go anywhere. I'm not saying that you have to agree with them, just listen to what they think. If you do listen to them then it will help you better understand where they're coming from. I know if I listen to some else's opinion I don't always change my view but it helps me kind of see how they might see it that way. If we can open our minds to new ideas then we just might beable to accomplish more things.