Maybe it's worth mentioning why we need to create an app registration in the first place:

Users are not able to directly use the Microsoft Graph API. This is because the Microsoft Graph API is intended for use by apps and services, not by individual users. When a user wants to access data or perform actions using the Microsoft Graph API, they must do so through an app that has been registered with Azure AD and has the appropriate permissions. This ensures that access to the API is controlled and that user data is protected. With an app registration, the app can act on behalf of users, but it is not intended for use by users themselves.