Employer is required to verify citizen or immigration status. For an American with a passport, the passport works okay.

Passport works great for ID all around, because it does not require SSN and does not have home address.

Many things, like TSA (Soviet era) checkpoints don't actually require ID. People seemingly prefer to act like cattle and show IDs everywhere and voluntarily consent to full body scans. Then people complain that their bits of privacy got leaked. Of course it leaked, and you voluntarily consented.

Elsewhere in this thread you're talking about birth certificates being voluntary (they're not). How are you proving citizenship for your passport without one?