Hrm. I, personally, don't believe that D&D is a good medium for adapting into cartoons or movies. What I've seen of said attempts, thus far, have been dismal. FWIW, I'm happy with any well-done fantasy that can be used to inspire D&D, rather than hoping the D&D will produce well-crafted fantasy films.
I'd be happy to be proven wrong, though.
Honestly, that would be what I'd want out of such products - not something that rigidly copies the game, but a well-done fantasy show/movie that includes elements unique to D&D. Either setting elements, or unique D&D monsters, or just outlooks that call back to the gaming experience.
Now, what would be the benefit of such a production? It's a good question, but I don't think that it is that hard to answer. As a gamer, I'd enjoy it (assuming it was done well, of course.) It would give me something in the media that felt crafted in part for me, and my recognition of the unique D&D elements would make me able to appreciate it all the more.
But outside of that, it would also help the hobby grow. The hobby being Roleplaying Games in general, and specifically D&D - kids grow up enjoying the show, or adults like the movie, and that presents an opportunity to bring them into the game and the hobby.
It sounds like you feel that media-related tie-ins to the game do not in any way expand the brand awareness or provide the potential for new players. I'm not sure what I can say to convince you otherwise. I would think it self-evident that more awareness of the game, especially in a positive light, would only help to draw in more players, and I think most marketing research would support this.
For me, that is why we should care. Being able to connect to other media can help expand the game. Having outside interests trying to figure out ways to make us happy and acquire us an audience can help provide us with better tools to play the game.
I mean, consider the scenario that someone comes along with a tool that would port over perfectly as a virtual game table, or some other new electronic tool that would be great for the hobby. Like something with the Microsoft Surfaces or some such. And they say, "Hey, we've got this product, isn't it the sort of thing we could offer to the RPG crowd?"
And so maybe they could go on to open up discussion with WotC, and this brings to the gaming community the VTT that many people would be eager to see, one professionally designed and developed. Or something like the Microsoft Surfaces D&D project, in a more portable or accessible price range for gamers. Or any number of other innovations or new technologies that might be right around the corner.
If those companies have a product that could be
awesome for gamers, but the perception of the gaming community drives them away, than that is a loss for
us.
Now, do we
need such products? Of course not - we already have every tool we need to keep gaming happily for decades to come, no matter what edition you prefer. That's one of the strengths of the game.
But it doesn't mean that new advancements and technologies to advance the game wouldn't be really nifty, and many of us would like to see them, and would hate to miss out because of a small but vocal subset of our crowd.
That's why we should care.
Again - the presence of those naysayers might not be a problem at all. That assertation has yet to be proven. But saying that even if it is, who cares? That the game doesn't need or desire advancements, innovations, or new technologies from outside? That's a really limited view, and not one that I think is good for the hobby.