” People get passports for their children just so they’ll have them.”
It was very unusual for children to have passports back then...!
There were exchange student programs she might have planned to be a part of. Some students in my high school were sent to school in Switzerland for a year. She lived in Washington - maybe she used her passport to go to Canada (she didn't need one, a bc would do, however it might have been an excuse to get a passport).
My high school (way back then) sponsored summer trips out of the country for students (my mom wouldn't let me go).
A passport back then was only 10 bucks and a useful form of identification both in and out of the country.