Because it can take a lot of time, and rip-offs abound, especially in major tourist areas. Business hours and holidays are not the same in other countries, and banks there may be closed when you least expect it. Also, many countries have no currency exchange facilities in airports, railroad stations and other points of entry. How will you get from the airport to where you're going if you can't change any money? When exchange facilities are available in the airport, lines are often long, and rates are often high. Your travel time is very valuable, and you don't want to spend it searching for a bank. Changing money before you go buys you peace of mind.

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