I guess part of the reason is that movies classified as "genre films" (comedies, fantasy, sci-fi, horror) are always viewed as being "lower entertainment" and are never taken seriously by critics, the Academy, etc.
I've always found that to be completely moronic, it takes just as much talent to make a really successful horror film as it does to make a 5-hanky weeper.
I remember being furious about critics and their "star" rating system. A movie like "My Left Foot" would get a 5-star review...while a sci-fi film usually maxed out at "3-stars", because the subject wasn't "worthy" of getting the highest rating.
Crap I say!