We are awash in fantasy films. Even Sword-and-Sorcery has a sizable number of entries (though generally of rather dubious quality.) Yet few of the S&S entries are adaptations of literary works. Why is that? There is no shortage of quality material to mine. Perhaps the producers determined it was cheaper to create a new property rather than license an existing one, thinking all you need is some muscular actor, a sword, a few scantily clad vixens, a malevolent, moustache twirling villain, some cheap, faux-medieval backdrops, and the script will essentially write itself.
How has that worked for them?