The files you create on your computers need to be backed up to another device in case something bad happens to your storage device. This could be theft, fire, hardware failure or other things. Ransomware is another disaster that may damage your files.
Cloud storage is a way to backup data and I use it for some things. My preferred method are local methods. I use external hard drives and USB drives for the majority of my backups. I like knowing I’m the only one that has access to my data. Things in the cloud are supposed to be secure but can the owners of the service prove it? I’ve heard of encryption with private and public keys, unfortunately I’ve never used this.