Here is a great list of reasons why you would want to shorten your URLs. Here is the abridged version of the list, but the link above gives a more detailed explanation, well-thought out and pretty obvious for anyone trying to spread their website by means other than links.
- Avoid broken links in your emails/messenger text
- Save characters in your SMS
- Tell others your links via phone
- Hide your affiliate links
- Much better for audio recirdings or repeating the URL over the phone
