It's a way of operationalizing what "working on yourself" might mean. Where to start, what to do next. There are other systems with other steps too, but this one is used in a lot of peer-supported addiction treatments and you can therefore get lots of good guidance and support in following them.
If your question is more "why do I have to work on myself", the answer is: are you suffering? is the way you are currently thinking, feeling and behaving making you happy? If not, then that would be the answer.
Best wishes for you recovery, whichever steps you chose to take!