I believe this is because setting (also called worldbuilding, odiously) is so much more potent in fantasy.

This focus on setting and magic can either eclipse the other elements, or enhance them.

Sadly 9/10 books in my genre seem to put such a heavy emphasis on setting that the rest is lacklustre either by comparison or because they ran out of creative juice. I can scream into the wind and say "make the setting reflect and support the character arcs" but a lot of people think the first priority of worldbuilding is to be 'cool' and 'original.' Therefore it ends up arbitrary, unfocused, yet interesting and cool enough to get a readership.

Also prose is inherently harder because usually theres no access to pop culture references in a secondary world. At least in West Wing they can quote shakespeare.