The average user already has created most of the accounts she will create. Outside of HN not everyone is trying out new services everyday. I could also see many people being confused by a random password and think to themselves that they'll never remember it and then override to use their trusty [but] insecure password. It's also not cross platform so not a solution for many people.

It's not Apple's fault, I'm sure it's a great password manager. The problem is passwords are broken. Managers are a good band aid, but fundamentally passwords are broken.