Because the reflex is to create a customer from every new email address. Within a year the customer list has hundreds of one-ticket entries, half of them colleagues of an existing customer.
A guest is somebody who raised a request but is not yet a known contact on a customer record.
Guests are held as requesters without creating an organisation. Domain matching suggests the organisation they probably belong to, and a person confirms rather than the system assuming.
Somebody from an existing customer's domain emails for the first time. The ticket links to that organisation as a suggestion; the agent confirms, and they become a contact with the ticket attached.
It will not assume a shared domain means a shared entitlement. Somebody from a large customer's domain may not be covered, and the agent is shown that rather than it being decided silently.
On confirmation the guest becomes a contact on the existing customer, and the ticket's entitlement and clock are recalculated from that point.
A default one, until they are matched to an entitled customer.
With a link to their own ticket only.
No suggestion is made; the agent asks.
Fourteen days, every module, no card. Or half an hour with someone who will run it on your own records and tell you where it does not help.