My best guess is that Apple won't do it because their plan is to phase out passwords entirely. That's what that whole FIDO Alliance (https://fidoalliance.org) is all about.

And 1Password is part of that too: https://blog.1password.com/1password-is-joining-the-fido-all...

I think that ultimately a password tool needs to be available on multiple platforms, like 1Password. Having it just be on Apple stuff just isn't gonna work for the many Windows and Linux machines I begrudgingly have to interact with.