Comment Re:I can't think of anything stupider (Score 1) 17
I think this is the latter case, where the backups are useless to signal or law enforcement, and can only be decrypted by the keys that you hold on your device (or in a backup if you made one). The keys get spread to all the devices you have logged in to signal, so if you have more than one you're reasonably ok to not make an effort to back them up explicitly. If you lost all your logged in devices and had no backup of the keys, their cloud backup would be useless, but it's not super likely I don't think.
It's absolutely the case that you could just use any random cloud backup provider, and that their service is basically an overpriced, limited version of what you can get elsewhere. But even with all those caveats, I think it's a pretty good idea for them to offer this service. Most non-technical people could understand how to back up their chat data to some other cloud provider, but they simply don't want to learn. They'd rather tick a box in the app and pay $24 per year forever.
Personally that's not me, sounds like it's not you, but I'm not offended that the option exists, and I think it's an ok way for them to secure $2 recurring donations in exchange for a token service.