We keep a Capital One Visa card for international travel to avoid repeated foreign transaction fees, and use it as much as possible.
But we still find a small amount to be handy in local currency upon arriving into a country for little purchases, drink machines, firewood, toll booths, museum admission, ferries, etc. Not everyone can accept credit cards, including some campgrounds.
Before crossing the border into Canada last time, we got $100 exchanged from US to CA currency at a bank in Machias, Maine. Glad we did, because I never saw a bank machine on Campobello island (though there may have been one) and it was a weekend, so many places were closed.