Other than airports I don't generally use it.

I look young and there's a lot of skepticism over age related purchases. When I do have trouble with my driver's license, the US Passport card looks official, has some security features that the NEXUS/GE cards do not (e.g. raised lettering for personal info), has the eagle, US stars and stripes, and the words "Department of State" on it, shifting hologram, etc. while not having my address - people see it and believe it's a real ID. Whereas they see the nexus/GE card and there's no obvious marks that it's issued by the federal government.