Apparently only 37% of Americans have a valid current passport
Even assuming that includes passport cards for Canada/Mexico, unless someone lives near the border, an international trip is a relatively big deal for a lot of families. The US is big and has a lot of variety for travel. It's really not surprising that a (sizable) minority don't have near-term plans to travel internationally.
Absolutely agree. The socio-economic breakdown of the research backs this up. It's very strongly correlated with household income
Seems there are some stats running around about the number of US citizens who hold passports.