Technically I suppose you wouldn't have to. But if you firmware update successfully following my steps, you will be using the latest firmware. What this does is adds new features to your machine that you might not even know exist. It could even solve errors that you might not know exist. For example, an update could increase GPS functionality which could result in a more stable flight - definitely a benefit. Another example, something you might not need, is that after one of the more recent H firmware updates we now have the ability to turn off the indicator lights on the H, which can allow for a less polluted image (for example: the blue lights could add a blue color to a picture at night).
Hope this helps! I would certainly recommend upgrading, because with every firmware update there is increased functionality.