It’s a good question. Aggregates make it easy for services to publish their current state (e.g. “User 123 is now in this state”), but as you point out, such messages don’t convey intent. If your Saga implementation requires a different message structure, then having Aggregate-oriented services won’t preclude that structure… and I’d wager, moreover, that your Aggregate’s well-defined scope would make it easier to design your implementation’s message structure.