Even if you loose all your remaining cash upon leaving, the price is small, if your overall goal is to get out and you have a whole life of income yet to make.
A friend of mine was walking through an air port and was asked if he was willing to be scanned with a hand-held device to see how much cash he was carrying. Apparently, the newer dollars have material embedded that allows for this. This was a little over 10 years ago. So, yeah. If you try to carry a large amount of dollars by plane, you may get detected and may face charges (I don't remember what the limits are.. maybe $10,000 or $20,000).
So, there is another dis-incentive to using U.S. dollars.