Because you tagged this question with "body", I think you are going for something different than what the previous answerers gave you.
Negative and positive feedback loops, when referring to hormones in the body, refer to decreased or increased production of something, usually a hormone, in response to some stimulus from inside or outside the body. There are more negative ones than positive, because usually the stimulus makes us perform an action that decreases the response to the stimulus. The overall goal is to maintain homeostasis--a constant internal environment. For example, an increase in blood pressure is sensed by sensors in the blood vessel walls. This is relayed to the brain, which sends appropriate messages to decrease heart rate.
I think that more specificity might be needed in the question as it is presently constructed. I can say that the need for negative feedback might be there in order to improve the quality of work produced. Especially so in the field of writing and verbal construction, nothing is perfect. Words and means by which to communicate are always, to a great extent, imprecise. What is conceived in the mind can never be fully and exactly replicated through words. There is always going to be some level of imprecision and this is the curse of language. Perhaps, this might be why negative feedback is so prevalent in that it seeks to clarify what our meaning can be through writing via an imperfect means. Essentially, we are left to try to improve or perfect something that is imperfect. In terms of science, I think that the notion of scientific collaboration and the search for the objective answer might be why there is more negative or constructive critique than positive feedback. The latter is present in the collaborative setting, where ideas are posted on a literal and/ or symbolic bulletin board for all to comment and absorb.
There is more negative feedback because we are always striving to be better. Correcting the negative things gets us closer to being our best. Yes, we all like to have positive comments, but that doesn't change us. It just makes us continue that good habit. Taking a look at something you do wrong can only change for the better.
THAT A GOOOOOOOOOOOD Question
i think it is because of MOST of us want a Perfect answers
Hope this helps