I see three main categories of people riding across the country: (1) young people between school and employment, (2) empty nesters who don't have kid responsibilities any more, some retired, some not, and (3) unemployed people between jobs.
And teachers with summers off. I love teaching HS math and an additional bonus was that I got summers off (after masters degree, certificates, etc). was able to live in the mountains and go hiking, biking and climbing with my kids.
John"s comments are good ones for those who are not teachers.