The reason it seems counterintuitive is because it is wrong as well as counterintuitive.
To help any economy, spending money of any kind does the job. You generally get a better deal in Jamaica by paying in J$. By law, all Jamaican businesses must accept the J$.
As a courtesy, many businesses accept the four main tourism currencies, US$, Canadian$, the Pound and the Euro.
Banks offer accounts based on all these currencies because some businesses conduct regular transactions with companies that only use these currencies.
With all this taking place, the idea that spending non-Jamaican currencies hurts the economy is illogical.
The majority of the time, foreign currency is exchanged at the nearest cambio. The average Jamaican has little use for non-Jamaican currency.
But if a Jamaican travels, having access to foreign currency can come in handy.
We have a US$ account to pay some of our bills, but the banks are limiting the monthly deposit amounts and adding fees and taxes on these deposits over the limits.
So with the current rules, spending US$ can actually create more fees for the banks and more taxes for the government.