Because a lot of people don't want to just "lube it up" and stick it in their butt; they want to buy a product that they like, even when it comes to looks, and are indecisive and want the reassurance of asking other people. For instance, if you're out shopping and you could get the red shirt or the blue shirt, but you can only get one shirt and you like them both, you'd ask for a second opinion, which can help you decide.
Sometimes people want advice, and sometimes people are farming for points, but really...who cares, unless it's just really annoyingly obvious? I've posted polls about lingerie sets that I'm unsure of, because I love lingerie, but can only get so many sets with my points. I like getting other people's opinions when I'm totally up in the air about it.