If the application works normally and it doesn't have any errors, then it's not necessary to fix something that actually works. However, updating the application to its latest version ensures that all possible bugs and flaws are fixed and besides that, you may have additional features implemented into the application to make it more user friendly. Practically, these is the meaning of an update. Although it is not necessary to update it, usually when you switch from a version number to another number (5 to 6) you may find that the program has completely changed. Switching versions sometimes means that you will be working with a new product with new functionality and features.
