Why no battling gods?

Troy, the movie version of Homer's The Iliad, is out today. Here is one report, from the May 14 Entertainment Weekly:

While Pitt's character got tweaked, the rest of The Iliad went pretty darn Hollywood. Briseis, a slave girl captured by the Greeks -- speechless in Homer's tale -- becomes a royal priestess and love interest for Achilles...More notably, no gods interfere with battles in Troy. "I didn't want them in," says screenwriter Benioff.

The screenwriter notes that activist gods would make the movie too much like The Clash of the Titans. My rhetorical question for the day is why clashing polytheistic gods make for a less broadly saleable story than do human heroes. And does this help explain why monotheistic religions have been growing at the expense of polytheism for some time now?

Thanks to Yana for the pointer to the EW article.