Why No Love for the SFF?

Why is it that scifi fans are so often NOT considered to be mainstream readers? Why do we get shunted around away from all of the "normal" book consumers and lumped with all of the fringe genres? Some of the greatest literature in the world has been written in the scifi/fantasy vein: Lord of the Rings, Hitchhiker's Guide & sequels, anything William Gibson, and so many others that it is impossible to list them all. How is it that works of this genre are so often shut out of the major awards? Not that the majors are all that matters because they aren't, but that doesn't meant that theses authors don't still deserve the recognition and therefore the sales boost. So many of them are immensely popular in Europe and get virtually nothing here. It's a travesty. Now, I realize that many authors don't want to be mainstream and have no problem with only reaching those who find them. That's their prerogative but as a bookseller, it's my job to try and introduce them to more readers when I know it's a perfect fit. But how can I do that when it looks like some of their covers were drawn by 3rd graders, approved by 5th graders, and then marketed by middle schoolers? The old cliche doesn't apply or else publishers wouldn't be spending oodles of money on covers and they would all look the same, so why do they instantly relegate SFF covers to ridiculous status? I hate it. Rant over.