We often create custom objects to bring together data from multiple standard/ system objects for various customer usecases.
For example, to merge data from Timeline and SuccessPlan together. In these cases, we are pulling all the required fields from both Timeline and SuccessPlan objects.
Instead, if there’s a lookup on to these objects based on the GSID field, we can pull the required fields based on the available lookups.
Our custom objects and rules become very compact if GSID is utilised fully for cases like these.