That was not my question.
In any case, I actually prefer it the way Signal does because
1) I don't have to sign up for / rely on a cloud provider,
2) if need be, I can decrypt the backup on my own and export it to some other format.
> then they only do backup manually
Wrong. The backup can be done automatically (i.e. every day).
Getting that backup off the device is yet another manual process for most users they need to think about.
Compare this to Telegram: user doesn't have to do anything.
Compare this to iMessage: user doesn't have to do anything.
Compare this to WhatsApp: user just needs to click agree.
The last two even save backups in an E2E encrypted fashion unreadable by servers.