And more importantly they generally don't have high university tuition bills that need paying. Since most people do this sort of travelling either just before or just after university, I imagine that is a pretty big factor.
Not always. Sometimes is something cultural. English people for example, they take a "Gap year" right after they finish high school and before they go to college. Most of the time they work during their last year of high school in stores, supermarkets, bars, etc. during the weekends to earn money so they can go on their "Gap Year" traveling to Africa, Asia or Latin America... where cost of living is much lower than in the UK and the money they have earned is enough to spend many months!
