I was gonna ask about the biometrics part in a separate question, but its both about security, so might as well combine it in one post.
Okay so I don’t use password managers. I just try to make easy to remember passwords 3-4 random words + 3-4 random numbers. Online accounts can’t be brute forced anyways. For offline accounts, I just increase the words and numbers. For mobile I don’t use biometrics, although I’ve been testing whether or not I want a pin + no biometrics or alphanumeric password + biometrics. I just can’t decide.
Several points
They generate strong passwords - completely random with no scheme or method to guess. They are long and use many different characters. These won’t be easy to memorize, but that’s the point of a password manager, isn’t it? Much stronger than “google-monkey123”, “lemmy-monkey123” etc.
They generate unique passwords - different passwords for every login. When, inevitably, one website had their database breached and it turns out that they stored the passwords too (you never store the passwords, only a “hash”, a scrambled version of it), that password of yours can’t be used on other websites. Or any scheme be detected “hey that guy just appends ‘monkey123’ to the name of the site!”
They protect you from phishing - consider this scenario: you get a message with a link, you click on it and the site asks you to log in, so you type in your login and password, but that was a phishing site, it looked like the real website, but really it wasn’t. And now the attacker knows your username and password. A password manager that automatically fills your login details will only do so if the domain name is exactly correct, on a phishing site it will not auto-fill, giving you a moment to stop and think.