Another perennial issue that never seems to go anywhere, most likely for the principal reason that, however bad the U.S. currency may be, it is usually in better shape than the currencies of most of the rest of the world.
Now, of course, the use of the USD as the currency of account is largely voluntary; however, in order to do an international deal, multiple parties are involved, including various middlemen, like shippers, and they typically want to be paid in a strong currency that isn't subject to the political or economic vagaries of the two countries involved (other than the U.S.), and may refuse to participate in an international transaction that isn't cleared in USD.