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.
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.
Yep, they’re allowed to run on Chrome, that’s Google’s platform.
Good luck using your Chrome/Google passwords outside Chrome/Google apps.
Firefox at least does (or used to) offer a Lockbox app to use the password on your phone.