[RedBeetDeadpool]

Because there are no dollars involved. If they do as you suggest, at the start:

A holds gold.

B holds dollars.

C holds oil.

A trades B, gold for dollars. A holds dollars, B holds gold.

A trades C, dollars for oil. A holds oil, C holds dollars.

After your suggested trade result:

A holds oil.

B holds gold.

C holds dollars.

If there is no "middle man", party A gets oil, party C gets gold. Party B keeps their dollars. End result:

A holds oil.

B holds dollars.

C holds gold.

Assuming "B" is USA, USA doesn't get to export its inflation/funding for stimulus checks/student debt/pension crisis/(or in trump era - a wall that does nothing) away to "C", whoever that ends up being, meanwhile, Ghana gets the oil it wants, and "C" gets currency without having to pay for the choices of politicians they have no control over.

[nickdothutton]

The US export of inflation via engineered demand for petrodollars (and one could say enforcement via aircraft carrier groups) is an under appreciated effect.

[luciusdomitius]

It is literally the most controversial concept in today's geopolitics. Study politics science in Dover - it is a conspiracy theory. Study PS in Calais - it is the exorbitant privilege and a cornerstone of global injustice. And it is not like France and the empire are rivals.

https://en.m.wikipedia.org/wiki/Exorbitant_privilege

[foooobaba]

Regarding France, actually they play this game too. Check out the West/Central African CFA franc [2]. These currencies are pegged to 1/100 French franc, which currently about 1/656 euros. Many former French colonies are required to use the CFA franc, minted by France, and required to keep 85% in reserve in French banks, including during times of hardship, but they can always barrow against their reserve and pay France the interest if they need to. In 2019 France has promised to drop it and let the africans have their own called eco [2] by 2027, but, also it keeps getting postponed and was supposed to already happen by 2020, so who knows. Trying to go against france can result in an assassination or coup, or other creative acts by france (see Opération Persil [3]).

[1] https://en.m.wikipedia.org/wiki/West_African_CFA_franc

[2] https://en.m.wikipedia.org/wiki/Eco_(currency)

[3] https://en.m.wikipedia.org/wiki/Op%C3%A9ration_Persil

[luciusdomitius]

Yeah, I know that. CFA Franc is exactly what they are accusing the Fed of doing, just without the good-doer facade. As ironic as it is :)

[rsync]

... charitably, I think your parent refers to underappreciation within the United States which I think is a fair assessment.

[nickdothutton]

Indeed I did mean in the US. The rest of us in the world are more acutely aware ;-).

[happyjack]

This! This is the answer! Trading in dollars creates micro transactions where the USA can export inflation and much of its problems.