Most of us can't remember more than one password. This means that if one site is compromised, then the attacker now has access to multiple sites. A password manager mitigates this issue.
People used to memorize the phone numbers of all important family members and close friends without much trouble. Anyone without a serious disability should have no trouble memorizing multiple passwords.
Sure, I do use password managers for random sites and services but I probably have at lower double digit amount of passwords memorized for the stuff that matters. Especially for stuff that I want to be able to access in an emergency when my phone/laptop gets stolen.
People used to memorize a few phone numbers, likely less than 10, and used notebooks made specifically for writing down phone numbers to keep track of the rest.
Phone numbers of the people you called the most (the 10 you memorized) were overwhelmingly likely to be local numbers, so you were only memorizing (3 number chunk) + (4 number chunk). Password rules are all over the place. Memorizing numbers, letters, whole words, the capitalization of those letters and words, and special characters, that are far longer than ye olde timey phone numbers, is orders of magnitude more difficult.
I have over 100 passwords in my password manager. They are all unique, so if any one is compromised, it is contained. My password manager is protected by strong 2FA, so someone would have to physically interact with my property to gain access. In the real world, there is no scenario where memorizing all your passwords is more secure.
They did not. They had papers with all those numbers written down next to landline phones. They also had little notebooks they carried everywhere with them with those numbers written down. You could buy those little notebooks in any store and they fitted into a pocket.
Moreover, those numbers did not changed for years and years. Unlike passwords that change, like, every 3 months.
"MyPasswordIsSecureDespiteNotBeingComplexBecauseItIsLong_BobsForum" is great until Bob's Forum gets hacked and it turns out that they were storing your password in plain text and your password of "MyPasswordIsSecureDespiteNotBeingComplexBecauseItIsLong_Google" becomes easily guessed.
You need a pattern that only you recognise/understand, not just remember. It takes only one leak of your password from service FooBar that looks like "f....b" to know what to try on other sites. Patterns easy to remember are mostly easy to understand.
