You need not know why they have this scheme, just know what version is the latest for your camera model and use that to keep your camera up to date.
Other camera manufacturers generally have just one firmware version to install.
The following links were recently current for the major camera manufacturers and may be of help when checking for releases of newer versions of firmware for your camera.
Read the instructions very carefully before updating the firmware on your camera – you don’t want to end up having a dead camera!
This topic is one that I often find myself explaining in more detail, and one that many people aren’t even aware that they can update their camera’s firmware, and how this may affect their digital camera.
An analogy is to updating the version of software on your smart phone.
Check the release notes that come with the firmware updates.
Usually you will find included a list of the fixes or updates in earlier versions of the firmware too.
This is called firmware and is the operating system of your camera which allows you to control the features and functions, with the camera’s menus and buttons.
If the battery fails during the firmware update or the update is interrupted in some manner, the risk is having a camera without usable software.
Meaning you have a dead camera that you have to take to the manufacturer to fix!
Look for higher version numbers than the one found on your camera.
If the version numbers are the same, there is no need to perform an update.