From what I understand the issue is more that people point domain to a DNS service, use it for a while and then remove their account (/domain from the account).

From what I understand the issue is more that people point domain to a DNS service, use it for a while and then remove their account (/domain from the account). Now someone else can add it to their account. This is unlikely to be an issue on their primary domain but could be for e.g. subdomains or some marketing domains that aren't really in use anymore. Or cases where domain is just be squatted.