We should be able to download snapshots, to store them wherever we want (and where it doesn't cost us money), and then one day, when we need to restore them, upload them. Note that there was already an "idea" for this, but it's impossible to find. See broken link here: https://docs.digitalocean.com/support/can-i-download-a-backup-or-snapshot/
It's actually pretty insulting "If you'd like this feature click here to vote for it: [broken link]".
Use case: I have snapshots that I took many years ago that I keep just in case I might need them one day if I find out that I lost some data that may be in them. It's costing me money to keep those snapshots that there's just a tiny chance I might need some day, so I would like to download them, and store them within the disk space of my current live droplet (or in a physical disk at my house for that matter).