It's not copy-pasted, it's scanned in once and never exposed to clipboard etc.

It allows you to keep your backup/storage of the key cold and only import one time, reducing how often your private key is exposed.

It also allows far more robust backups as you just leverage your existing backup infra for Bitcoin keys (Nostr key is derived from your seed).

Until key delegation is widely supported this is by far the best approach IMO.