A browser is a platform. I have no easy way to use passwords saved in Chrome in Safari for example.
It matters to me because I use Firefox and Chrome on my work desktop, Safari and Firefox on my personal desktop, and Safari on my phone. And I want the ability to switch browser easily.
Same goes for Apple passwords, I still use Windows for some games, and I want to access my passwords easily.
Apple is the only one of those three that restricts their software to hardware that only they sell. So in that case I do understand your position.