Incidentally, a Microsoft Passport login still works on any site with today's "Login with Microsoft" ... and there are starting to be more along side "Login with Google" or "Login with Apple".
These days, a consumer + biz page login page can look like this:
There's almost no good reason to require emails/password rather than let users use their preferred IdP.
I think the reason it's less common is simply that indie devs assume everyone uses free Google Workspaces. This year we're seeing more Microsoft Logins. Perhaps one reason is that now Google Workspaces is no longer free and startups are realizing they can get actual Office with actual apps at the same per $6 to $12 per user cost. Then in turn, supporting that login.
These days, a consumer + biz page login page can look like this:
https://www.xsplit.com/user/auth
There's almost no good reason to require emails/password rather than let users use their preferred IdP.
I think the reason it's less common is simply that indie devs assume everyone uses free Google Workspaces. This year we're seeing more Microsoft Logins. Perhaps one reason is that now Google Workspaces is no longer free and startups are realizing they can get actual Office with actual apps at the same per $6 to $12 per user cost. Then in turn, supporting that login.