For much of the world, vegetarianism is largely a matter of economics: Meat costs a lot more than, say, beans or rice, so meat becomes a special-occasion dish (if it's eaten at all). Even where meat is more plentiful, it's still used in moderation, often providing a side note to a meal rather than taking center stage.
In countries like the United States where meat is not as expensive, though, people choose to be vegetarians for reasons other than cost. Parental preferences, religious or other beliefs, and health issues are among the most common reasons for choosing to be a vegetarian. Many people choose a vegetarian diet out of concern over animal rights or the environment. And lots of people have more than one reason for choosing vegetarianism.
