Until Google, or Apple, or facebook, or whoever is the passkey store holder decides to put up an interoperability wall, either through neglect, cost savings, or

Until Google, or Apple, or facebook, or whoever is the passkey store holder decides to put up an interoperability wall, either through neglect, cost savings, or intentional user retention. The big providers could provide cross company SSO (e.g. sign onto my google mail account w/ my apple identity) for all their accounts already, but for some reason that hasn't happened...