Why would you have unsuccessful tooth extraction?

Not sure: If the tooth is removed, then the extraction is successful. There can be instances where for various reasons, the dentist may need to leave a small piece of tooth. Usually there would be more damage in removing the small piece rather than leaving it. However, a patient should always be informed if this is the case. In addition, follow up care may be needed if a piece of tooth left causes issues.

Sometimes: A fragment of the root tip can break off and may not be able to be retrieved readily (ex. For fear of pushing it into the sinus if it's an upper molar). The body often will accept of this fragment without the patient experiencing a problem. But the patient should always be advised of that and treatment options recommended to the patient.