Because you're missing the whole point. Password managers are there so you can generate a password like G&li/PdsZH-)73m?Df78:+pJS*(9dD79. You don't have to remember it and the password manager "should" be secure and encrypted. The Password manager will auto fill in the password across your devices so you don't need to dig out your notebook and type that thing in. You also wouldn't be able to log into your bank account app, or other apps or websites from your phone if your password isn't saved unless you always carry that paper with you.

Then, there is the sharing part. I share passwords for sites with members of my family. I have to share thousands of passwords with members of my team at work. A shared vault that's encrypted and secure works great for that.

Paper is great for my mother. 1 computer in her house, doesn't use her smartphone for anything smart. Wouldn't need those passwords away from home. Doesn't need to share. She actually uses an address book with the little alphabetical tabs. If she needs her google password, she flips to G.