The point would largely boil down to being a good citizen and reducing abuse, like making your domain less useful for spammers to impersonate and to make it immediately clear to others that mail is not deliverable there.
If the claim is accurate that the domain is not used for either sending or receiving email at all, you could add something like this:
domain.example. IN MX 0 .
domain.example. IN TXT "v=spf1 -all"
_dmarc.domain.example. IN TXT "v=DMARC1; p=reject; aspf=s; adkim=s;"
This indicates that inbound mail is not accepted (null MX), and that any mail sent from the domain should be rejected (SPF policy that lists no allowed senders + DMARC policy enforces From-header alignment).