When a tooth has been damaged to the point that we can not save it by doing a root canal which is the last resort for saving a tooth, then extraction is needed. If extraction is needed, then you need to replace that space as soon as possible so that the teeth don’t start to shift into that space. Some of the options to replace the tooth is: Implant, Bridge, or partial.
Another reason for extraction is extraction of wisdom teeth. Many people don’t have enough room for the wisdom teeth to come in and it end up to either be impacted and need surgery to remove them or they can erupt partially or malposition.