There many varied reasons why people can’t/don’t travel. I think many of them are variations on the same theme – fear.
People are scared. Scared of the unknown, scared of failing, scared of looking foolish, scared of deep water, scared of snakes, scared of heights, scared of being robbed, scared of not knowing anybody, scared of not knowing the language. Scared of getting out of their comfort zone.
Fear generates lots of excuses and people are really good at finding ways to chicken out.