They've been used a lot but with respect to Iran, they also consist of secondary sanctions -- meaning that the US not only refuses to do business with Iran, but also refuses to do business with any third country that does business with Iran.

In the 1970s the Arabs imposed similar secondary sanctions on Israel, and the US was morally opposed to secondary sanctions since they violated the principle of free trade and were an effort to impose sovereignty on other nations -- which is why the US laws prohibited any US country from observing these Arab sanctions...

But when it came to Iran, the US was suddenly a fan of secondary sanctions.