1. You have duplicate content
Duplicate content is that it appears more than once on the page. There are multiple pages on Google that contain duplicate content. In this situation, it is difficult for Google to understand which page is the correct one. You can use a 301 redirect on the duplicate piece of content to direct to the original page. It will create a better experience for your users and help to improve your search engine rankings.
2. You have changed your domain
The use of redirect is useful when you are making change your domain name and probably do not want to lose any built links.
3. You have multiple domains
To protect the online brand, some people purchase multiple domain names. So, they will need to redirect any of the old domain to the new domain. Many companies do this to gain additional traffic from common misspellings. Also, they can prevent competitors from buying a similar domain and can redirect them to their own site.