Just as you should update your computer, accounting software, or Microsoft Office suite to take advantage of the latest features and program code changes, you also need to update your WordPress software. You don’t have to update it for every single version that is released, but it is wise to do so at least once per year.
I had a client contact me in a panic recently about his website disappearing. I later learned that there he had not logged on to his website at all in the last year, which means that he had missed every update message that would have prompted him to run the updates and prevent this problem from happening. Although this is an extreme case, it serves to note the importance of updates.
If you continually use an older version of WordPress, you run the risk of things going wrong.