[dheera]

- Business: Legit customers sometimes guess e-mails like support@, abuse@, sales@, jobs@, careers@, info@, and other language variants of these words, you may not want to set up mailboxes for all of these.

- Personal: Plus addressing doesn't work with many services but you sometimes want a single-use e-mail address to purchase something from a website and still have the receipt.

[svjx]

Yes, we know that plus addressing isn't always supported. That's why we have subdomain addressing which is really its successor.