Why don't we ever get to see animated versions of, like, Paradise Lost?

According to AnimeNewsNetwork, anime director Osamu Dezaki is planning to debut his anime Genji Monogatari Sen-nen-ki Genji ("The Tale of Genji: A Millennium-Old Journal") on Japanese television in January.

Originally, this adaptation planned to focus on Waki Yamato's historical shōjo manga Asakiyumemishi - The Tale of Genji (another a retelling of Murasaki Shikibu's The Tale of Genji), but Dezaki apparently decided to go straight to the source. His anime will celebrate the thousand-year anniversary of this classic Japanese novel.