Reborn a Mac,
You make a sound argument for using the Keychain Access app on the Mac, and using Settings-> Passwords on the iPhone/iPad.
While this is a basic password manager, it should be sufficient for many users, ESPECIALLY if they use the ‘Notes’ field for supplementary information, such as password recovery questions and answers, contact phone numbers, etc…
And if a user just needs the basics, it should work very well.
But on the iPhone/iPad it does not support storing secure notes with images, such as drivers license, passport, etc …
And while you can finagle text information, such as credit cards, social security numbers, badge numbers, building access codes, etc… it does not make that as easy as a full service password manager.