You should keep your web browser up to date for several reasons.
For latest features .
If you don’t use the latest version of your web browser, you probably miss out on some features. More than ever, websites are taking advantage of the new features that modern web browsers provide; HTML5 video and audio.
To stay safe and secure at all times.
If you run a web browser that is out of date you risk having your computer compromised by criminals. If your computer’s security is compromised, you risk being used as a "middle man" in online crime; or as an accomplice in large scale attacks against other internet users or companies. This is not a hypothetical event. It happens regularly and in large volumes.