being able to restore immediately to an S is a lot safer than restoring to a software wallet and is a lot more convenient than waiting for delivery of another wallet.
This. A secondary Ledger device is just so you have a backup device where you can enter your recovery phrase safely by entering the words on the Nano S itself(not using a keyboard), whereas if you enter your recovery phrase on a mobile/desktop wallet, your recovery phrase can potentially be exposed to a hacker/s.