I don't really see it simplifying a lot of internet. Everyone will make his custom login page anyway, you need to add links to registration, password recovery and so on. And sending password on every request, hashed or not, is just bad security, you need session token anyway.
I think second party controls are probably the reason why browser intermediated login was never pursued until the present era of password management--the browser is a third party that can facilitate/intermediate communication between the first party (user) and second party (website). It would be foolish for a website operator to hand their users over to Microsoft back in the day, just as "social login" is a convenience/optimization trap today.
