Because it looks awful...
Really? Because I didn't even notice it when I saw the film in the theater. It was only when people here pointed it out that I even knew about it. And it certainly didn't ruin my enjoyment of the movie upon repeated viewings.
...plus, with the big ass budget the film had, a decent engineering set could have been made. The brewery makes me feel JJ was either cheap, lazy, or thinking the innards of all vessels, sailing or space, are going to look the same for centuries.
I'll admit that it would have been nice to have a really cool futuristic-looking engine room for the minute or so out of the entire film's running time that we saw it. But I'm sure JJ felt that it would have been a waste of budget dollars to build such a set when we only saw it for a few seconds, and then maybe three minutes tops when Kirk and Scotty beam aboard.
Dukhat, the brewery, I think, will be a piece of ridicule and amusement in Trek history, up along the likes of the entire concept of "Code of Honor", the phallic rock in "What are little girls made of?", TNG sets on ST6, Crosby's acting in season 1 of TNG, and "cupcake" and Scotty's goblin sidekick in JJ's film.
That's the thing, though: There's a world of difference between ridicule and amusement, and downright vitriol about an insignificant piece of Trek history. If someone wants to have a chuckle about the brewery set, fine. I've even joked about it myself in the "Budweiser's Back" thread. But it didn't completely ruin my enjoyment of the film, and certainly doesn't warrant such idiotic rants as what it's been given by some people here. Yeah, I think "Code of Honor" was stupid too, but I don't constantly post on the TNG forum that I think it's a piece of shit that totally ruined my enjoyment of TNG for years afterward. Because it didn't. And I wouldn't do so even if it had.
You want to know what I think? I think that ST '09 haters just focus on the brewery in order to bitch for the sake of bitching. Just like that William Wallace guy who joined the TrekBBS solely for the sake of pointing out insignificant "plot holes" in the movie, and then promptly disappeared once he couldn't do it anymore. It gets really old really fast.