Why Model Item is interfaced in IB for a configuration?

Hello,

I want to understand the reason why model item is interfaced to IB when a configuration item is shipped to customer.

When a configuration item is shipped to IB, instance relationship is created as

The example of ATO model after configuration

              Model Item (No Serial)

                      - config item (Serial Number present)

                              -Option Class1

                                         -Item1

                                         -Item2

                              -Required Item3

All the transaction from customer perspective are done on the configuration item. Model item is no where needed for transactional purposes. So, why does it get interfaced to IB?

Thanks & Regards

Sourabh