You say it as if unsharing by moving an item from an organization back to an Admin or Owner is equivalently or less privileged than deleting an item. Whilst this is true on a technical level, it’s not on a social level (and password management is as much about the social as the technical).
If this functionality was implemented, then Admins/Owners would unshare items and then carry on using them as personal credentials. But of course, once credentials have been shared to an organization, you have to assume that anybody in the organization could have access to them. This is dangerous. Whereas deleting an item has a completely different use case - it’s for when an item is null, void, no longer needed. If the account for the deleted item remains, then it is self-evident that the credentials must be changed before the item is deleted. But for unsharing, this is not the case and would cause issues.
For some people and organizations, the way that Bitwarden handles this is preferable. For others, it is not. The only way that Bitwarden will accommodate both viewpoints is with a deeper toolset of enforcement policies and access controls that enables both workflows to be achieved.
But guess what, at this point it becomes another CyberArk or Password Manager Pro. Is this what Bitwarden is supposed to be? Enterprise bloatware with a gazillion options to configure before you can even get started? I don’t think so.