Probably because we have a country that is massive in scale. My nearest international border that I can drive across is 1,120 miles away from me.
And we've got 50 different states that are, in effect, their own countries with different cultures to experience.
Why do I have to go to Paris, London, Beijing, Kathmandu, or any other international city when I'm never going to see all my own country has to offer unless I just want to?
I’ve spoken to a few Americans about travelling/holidays (vacation) and a lot of them don’t even have a passport
Why is this? 90% of Europeans have a passport