Prior to iOS 18.1, Apple did not allow users to delete, change, or turn off a primary iCloud Mail address. You could set an alias and use that instead, but the primary email would still sometimes be visible to others. For those who have an embarrassing iCloud email address, there's now an option to change it entirely rather than relying on an alias.
I can finally ditch my dead name email address. Saves me the trouble of creating an new account.