Obsidian is your personal wallet for OTP tokens. Nowadays many services offer 2 Factor Authentication (Google, Facebook, Amazon, Github, Digital Ocean etc.) so it’s good to have all your tokens stored securely in one place and available on all your devices.
The purpose of 2 Factor Authentication is to increase security, for this reason, Obsidian relies only on the Apple’s iCloud Keychain to share data between devices. There is no third party server where your tokens are stored or pass by!