Why Aren't There More Sci-Fi Movies About Dreams?

In the recent movie Coma, everyone who falls into a coma finds themselves inhabiting the same surreal landscape. Science fiction author Anthony Ha enjoyed the film's premise, and is surprised there aren't more science fiction movies about dreaming. "There isn't quite as much as I would have expected," Ha says in Episode 441 of the Geek's Guide to the Galaxy podcast. "There's so much dream fantasy fiction--and certainly there are a number of science fiction examples too--but it seems a lot less common." The best-known science fiction dream movies, such as Inception and The Cell, are at least a decade old, and the best-known novels on the subject were published in the 1960s and '70s.