I make sure to have a regular passport and the passport card. If I am not driving a car, then those are my identification and they are legal identifications per federal law period, end of story like your military ID card.

The advantage of the passport especially the card version is that while it is a legit federal ID, it is only accessed through much more restricted databases than a drivers license and therefore nearly useless to the municipal/civil interface of credit, banking and residence verification. That's what would make identity theft and fraud much more difficult, not to mention personal stalking.