For the same reasons that I split up the `objs` list: (1) That would be compressing the representation earlier than necessary, making it harder for the user (and the GUI) to work with. e.g. if the user wants to do their own visualization / storage / analysis of the model, it becomes more difficult. (2) I don't like having heterogeneous data containers, because you have to do explicit type checking when it comes time to use their contents. (3) You don't actually gain very much from having everything in the same list. It's not as though the number of different lists is expected to grow at a significant rate (or at all).