Companies implement SSO to have control over the accounts of their employees... Pretty sure they would still do it if it was more complicated.

And that is also why companies don't allow employees to use anything other than the SSO.

Well, it gives you easier control of your accounts too. Just one entry point for everything, no need to track password leaks from dozens of services (you still need to keep an eye on whether Google has leaked your password, but in that event everyone will know and be working hard to fix it).

From the point of view of technical people it would be easier to achieve the same with password managers, but for the rest of us Google provides a smoother user experience.