If you run a site, having a backup is something very necessary, especially if you have important data or you have invested time and cash in creating the site. There are various situations why you may need a backup - if you update a script and something fails, if you eliminate a file or a whole folder accidentally, and so on. Having regular backups will help you avoid any loss of information or at least minimize the damage, which is still better than losing the entire site. You could download a copy of your content on your computer occasionally, but as you can't do that after every single change, you must rely on the backups which your web hosting provider generates. Since that is something extremely necessary, you must make sure that they keep up-to-date backups, because a backup created once every one or two weeks might not do any good in case you run an Internet site like an online store or an accommodation reservation portal.