> versus fiction in a fantastical world or a "real world" where the existence of magic™ must be extensively explained.

Well now if we're drifting, I don't consider "fantasy" has to explain everything like it were an AD&D manual.

Take Glen Cook's Black Company series where magic just happens without explanation. Compare with something like Brandon Sanderson who describes "magic systems" in great detail always. I find the former enticing and the latter boring.

Lord of the Rings didn't explain anything either.