Respectfully, I'm going to have to disagree about stock Windows working fine. There are multiple places where it necessitates having a keyboard and/or mouse connected.
- Interacting with UAC prompts and other elevated-permission windows that block synthetic input events.
- When a popup hijacks focus away from the game window.
- When Steam (or other controller to mouse software) is not open, such as during the logoff screen where you sometimes have to click "Close Anyways".
- After a BIOS update, when the TPM refuses to unlock and you need to enter the BitLocker recovery key within the pre-boot environment.