This approach leverages the existing data flow patterns that marketing automation platforms already use to write to Lead and Contact objects. We build on these established processes to capture interaction data.
Writing directly to the Engagement object would require external systems to handle complex logic around:
Determining if an Engagement should be an Activation or Influencing Engagement
Establishing proper relationships with existing records
Managing data validation and business rules
Handling edge cases and error scenarios
By using Lead and Contact Processing Fields as an intermediary, we keep this complex logic in Salesforce where it belongs, while allowing external systems to continue using their standard integration patterns.
For more details on how this data flows through the system, see Processing, RAW, and Reporting Fields Explained.