Earlier quoted context omitted.
You won't get anywhere with a $100 bill in many developed countries, outside of some very tourist-y areas maybe. At least not in regular shops, of course you can exchange it at a bank. But if you try to order a coffee with US dollars, you won't get one.
If I’m visiting a country it’s usually as a tourist. Even on my business trips I spent half the time being a tourist.
The places where I've seen this mostly work was near borders, and it makes sense that you'd accept the neighbour currency there even if it is some overhead. If you can quickly hop over the border you're much less likely to exchange currency before than if you plan a full trip in a different country.