US Medical Insurance Costs project: why should dictionaries be helpful here?

I would like to understand what are the advantages of creating a class and a dictionary for this project. I first did the analysis just using lists and for-loops without defining methods and writing indeed less code. I see that the code gets more tidy and the analysis easier to follow when introducing a class and defining methods, but are there other reasons for doing that?
In particular I really don’t see the advantage of introducing a dictionary when the data are stored in lists, and can be addressed using the list index.
Thanks for your help :slight_smile:

Link to repo: