Why Do Backups?
Probably the most sensitive part of any WordPress site is the database. Plugins can be added back, themes can be re-installed, but if your WordPress database gets hacked or is corrupted then you are in big trouble. The database is where all the irreplaceable stuff is kept. Your posts, your pages, your content, your comments, everything that makes up your WordPress site is in the database.
*I can personally attest to the fact that loosing your WP database can be a disaster of monumental proportions.* Mike S.