It's quite different from use one password everywhere. My threat vector I wish to protect against that some random website I signup to will mismanage passwords and end up with them leaked, causing every website using that password to be compromised. Remembering hundreds of unique passwords is unreasonable, thus, password manager.

Considering the amount of times my email has ended up in a leaked dataset, and the only accounts I've ever had visibly compromised were ones I did not use a password manager for, this seams to be the correct mindset.