World of Warcraft has a long and fine culinary history and it's for more than just show...cooking has become intertwined with the actual play aspect, as food is an important consumable for running end-game instances, especially raids.
However, Blizzard appears to take the position that only meat and fish can get a fine blood lust (not Bloodlust[tm]) going in people. While I fully appreciate the powers of protein, characters are probably getting enough protein from all the non-buff food that they can be assumed to be eating to fuel their metabolism for all the non-instanced activity they engage in. It's also to be expected that characters are mostly carnivorous. To my eye, the lands of World of Warcraft are significantly less agrarian than our real world.
Fruits and vegetables obviously have virtues, as well, though. Why shouldn't we have some vegetarian buff foods in addition to the meat- and fish-based ones? Let me be clear: I'm nothing even remotely resembling a vegetarian in real life. This is not a "Blizzard, validate my life choice!" rant. This is just something I thought about and thought was fun.
Currently, buff foods mostly come from fish and meats, which require farming. Now...where might we find vegetable matter that can be farmed? Herbalism? That was my first thought...why not allow for cooking recipes that require herbs? Of course, the main drawback to this is that any character can pick up fishing or kill beasts that drop tasty meats. Any character cannot pick up herbalism, as not everyone wants to be an herbalist. It may not be ideal to have some foods depend on a primary profession.
But Blizzard could always institute a pseudo-herbalism. Humans (and humanoids) are inherently hunter/gatherers. Currently, most of our gathering is strictly the gathering of loot(z). Why not be able to gather fruits and vegetables? Blizzard could create a new set of nodes that are based on a secondary profession to gather. I don't have a good name for it, at the moment. Like fishing, you'd skill it up through gathers (though fewer gathers per skill point, since you're not able to sit in one spot to do it) and higher level fruits and vegetables could be used in higher level foods.
And if Blizzard ultimately wanted to incorporate herbalism into it, I don't think it would really be a problem. Food is never soulbound and most people don't skill up fishing on every character they play. Just as you may have a fishing character who sends the fish or the completed food to your raiding main, you could have an herbalist character who sends the herbs or the completed food to your raiding main. And if you just refuse to skill up herbalism on any character (I just did it the other day, it took less than two days to do!), there's always the auction house.
Some foods, maybe even more powerful ones, might use both fish/meat and herbs. Wow! Fancy. I hope I didn't just blow your mind with the complexity implied here.
I think it would add one more (slight) level of depth and a little bit more fun. One more way to do the things you already do: grind, make stuff, kill bosses.
On the other hand, maybe it's pointless because why add another thing to grind and make, when all we want to do is kill bosses?