Temporary email is badly needed: If you work in social media marketing to create multiple social media accounts. If you do not want to "shine" your real Email address on various Internet resources.
If you want to remain anonymous on the Internet, but access to some sites and services requires registration. If you do not want to receive spam and annoying mailings to your main mailbox.
Sometimes we all need a five-minute mailbox. Register on a forum or some site just to download some necessary program or for "one-time" correspondence with a person who does not want to give his main eMail. In such cases, temporary e-mail services come in handy.