It is important because as you write the paper you get more and more involved and sometimes a new person gives a different perspective that you wouldn't have seen on your own. It is also great for those pasty grammatical errors. Even if you feel the paper is solid having someone else look through it will find the little stuff that adds up!
It is interseting to see how other people think, and sometimes they find stuff on the internet that I didn't find when searching and it can be a real help.
I like to hear what other people think. That's why they have customer service, even though sometimes the customer service is bad, lol.
Feedack s important because if you don't know whats wrong with your paper and someone else looks at it they have a diferent point of veiw and may be able to see whats wrong withit its important in the revising step