I don't have hard numbers, but as a frequent traveler, exchange fees are honestly pretty annoying, so much to the point that I manually exchange money with wealthy friends in destination countries, horde cash like Japanese Yen in a box until I go back, and other nonsensical-in-2015 things.

A lot of countries still operate on mostly cash (like the aforementioned Japan) so getting by with only a CC isn't too feasible. Then, relying on the ATM will cost you a lot of money over time unless you specifically have a checking account at a bank with no ATM fees.