They have everything else, so why not this?
Most Helpful Girl
Same reason GAG doesn't have a dislike button. Some one may get butt hurt if you dislike there opinion.1
Most Helpful Guy
Probably because it's not an advice site, it's an online public diary.
So imagine the scenario, I post the following:
"I GOT A NEW PUPPY! LOOK HOW CUTE IT IS!"
150 people disliked this post.
How would that make people feel? It would make them feel like shit, wouldn't it.0