Your Websites contained valuable information about what you do and sometime more valuable than the money you have. Because you can struggle to earn money anywhere but some important files and records cannot found anywhere. Some files cannot be retrieved forever. The resources used to gather all the information, like time, funds, sleepless nights and technical personnel envolved, cannot be easily to have the same chance to have the whole thing at a time.
To have some data back, you have to struggle for many weeks, months or years of exercise. You can save your grief by making multiple backups as the there is no single backup that is 100% reliable. To have a backup on your site is GOOD, to have multiple backups is BETTER and to have a multiple backups at different locations or regions is the BEST. You may have Virus infection, Hardware failure or server crash, backup is the only convenient solution.
Making backup whenever you want to make update before and after any physical changes backup is necessary if you want to secure your site and files, with such precaution you can reverse any changes easily as well as updating your backup with recent or additional data.