Apple issues app-specific passwords for the same reason Google does: so mail clients and integrations that don't support Apple's full sign-in flow can still send mail through iCloud's SMTP servers securely, without exposing the main Apple ID password. This account ships with an app password already generated and documented.
It's built for developers and marketers who need a reliable SMTP relay for transactional or outbound email and prefer Apple's infrastructure over Gmail's. Works with standard mail clients and any SMTP integration that accepts a username and app-specific password.