Yep. If you travel to Cambodia in the tourist places you will see everything priced in local currency. I remember noting the weirdness of it when I was living to Hong Kong that I had to change my HKD to USD to spend in Cambodia.
I strongly suspect it is just for the convenience of customers. Local businesses pay the cost of converting it into local currency.
But certainly in many places I have been, local currency is subject to foreign exchange control, and so foreign tourists are reluctant to change a lot of money in case they cannot change it back. Accordingly, people who work in the tourist trade accept USD or other international currencies to help make sure that the tourists keep spending.
