- You may not have all your source code repos synced locally. Maybe you think you do but forgot one.

- You may keep your phone in your computer bag and lose both at once (both your 2fa and your code).

- You may drop your phone in the ground and fail to get access to your password manager.

.. etc.

Having a backup strategy which involves you not breaking a piece of glass (aka phone) you play with while sitting on the toilet is a bit risky.