AFAICT an order's status isn't visible to the customer. I created an order, then as an admin cancelled it, and the user could still see it but there was no indication it had been cancelled.
This is required in a number of scenarios:
- store staff cancel an order due to stock or payment problems
- an order's payment is something that's not immediate, such as cheque, invoice, or account payment. It's useful for the customer to have a reminder of this when they view their order.
In most cases the user should get email notifications too, but having this on the site would be a useful reminder, and probably save store staff from dealing with support emails and calls.