Suppose you set up shop in the US and hire some staff. You see some activity in France that you’re sure will produce exceptional returns, so you convert all your USD into EUR to invest.
At the end of the month, your staff want their wages, but your capital is tied up in EUR and it needs just a bit more time to start generating cashflow. So you really don’t want to sell right now.
What you might do instead is to borrow USD against the EUR investment so that you have some funds with which to pay staff.
Note: if you're borrowing, you should expect that the lender will one day want their money back. If the EUR investment doesn't pay off, you might end up with a loan but no capital with which to repay. This would be bad. Don't engage in it without seeking competent financial advice.