Maybe there are technical requirements of which I am ignorant, but I find it so annoying that Treasury went this route of paying a private sector vendor for identity and login management when login.gov exists.

Screenshot of email announcing the U.S. Department of the Treasury is announcing that starting September 13, 2026, TreasuryDirect will implement a new login process using the secure identity verification provider ID.me.
Nic Babarskis @thebigbabooski