The main culprit behind the international growth of DCC are Visa and MC. Both have been pushing merchants to buy into the practice. The argument is that a merchant using DCC is better than a merchant who doesn't accept plastic at all, but it remains entirely dishonest.
Some cities/countries are worse than others. I lived in Italy and rarely saw DCC used (with the exception of hotels, which often ask... I'm looking at you, Westin Excelsior). A week in Dublin, though, was DCC central. Nearly every merchant, except Trinity's bookstore, tried to get me to use it. A coffee shop didn't give me a choice and a call to Chase got the difference refunded. I quickly learned to say "charge me in euros" as I would hand over my credit card.