Many people prefer to back up files to iCloud because they found it better and faster but the thing is that backing up to iCloud may not always be that successful especially when network problems strike. When this happens, your next option would be to back up files manually. And this is where iTunes play
Although your iPhone is equipped with great security features, it doesn’t guarantee that all files you store in it are always safe. Thus creating backups is highly recommended. Among the usual instances when backup creation is necessary would be prior to installing an iOS update, resetting iOS to factory defaults, and restoring iOS via iTunes.