The factual answer is that the FCC is driven by listener complaints. If they get a complaint letter, they take action, if they don’t get a complaint letter then they do nothing.
Spanish speaking people who hear curse words in spanish language broadcasts are very unlikely to write a complaint letter to the FCC, for lots of reasons that shouldn’t be too hard to understand. The person might not speak english well enough to want to try to write a complaint letter. People from latin america don’t have the expectation that a complaint letter to the government will do much good. Lots of spanish speaking people are here under circumstances where they prefer to remain invisible to the government, and that attitude seeps over even to people here legally.
As for non-english curse words used in english broadcasts, again, someone has to complain. If that Bible-thumping biddy who listens to Howard Stern hoping to hear a curse word so she can write a complaint letter to the FCC hears the word “schmuck” and doesn’t percieve it as a curse word, she’s not going to write that complaint letter about that word.
