Honest question: Why does any none need password managers? Does not chrome password sync or firefox sync do the job? Thanks

Chrome and Firefox are password managers :)

People use other managers for many reasons: storing passwords (and other secrets) which aren't used on a site, using them on different browsers (say, Safari on the desktop and Chrome on mobile) and lack of trust on the browser's password manager.

Also, for a long time, browsers didn't save passwords with forms marked with autocomplete=off.

To generate random, strong passwords. Also not to be locked into a browser. Better actual password management (e.g. last changed). Tags.

A canary of chrome did have the ability to generate random passwords, but password management in chrome is still a pain IMO. Not sure about FF, but a quick google suggests it doesn't generate random passwords automatically.

FF doesn't, but as usual, there are addons for that :)

Some of us still use native applications that don't use Chrome or Firefox.

Can any open source password managers do this?

When I used pwsafe and keepassx they had this option.