Looks to be the USA equivalent to the GOV.UK One Login system which is also being pushed. Good to see goverments trying to working across departments to make things, eventually, easier https://www.sign-in.service.gov.uk/
It has that because of political will to implement it, combined with a coherent design language implemented as a set of well-thought-out components. It is a "pit of success" - departments get better quality for less expense, so they don't chafe about it being mandated.
I don't see the political will in America. The population hates anything that the other side touched. "The proud state of Mississippi was built on jQuery", etc.
I personally used it for global entry and I have seen it used for the PPP site during covid