Whatever data I have backed up in the cloud is synced across multiple devices that I use. Even if the cloud disappeared altogether, I still have it. The cloud allows me to keep an up to date copy across various devices.
I highly suggest everyone disable this setting on their own, but also on their (perhaps less technical) friends' and relatives' devices. Otherwise, if anything happens to your account or - less likely - the storage provider or their hardware, your data could very well be gone forever. I can't believe anyone would want that.