Feedback is one of the necessary condition for people to take his  responsibility.
When you grow up and you have the freedom to decide your dress, a mirror can help you to dress well, because it give  you the feedback of your appearance.
Study is a thing that need people to be responsible for himself, so we need feedback. An accurately, completely, timely feed back will be more helpful.
Examination is a tool that can give feedback of your study, but only provide the mark of your paper is not enough generally. It depend on the difficulty of the examination and the
knowledge of people.
A speedy calculation exercise may not need answer, because we can get necessary  feedback by check it  carefully when we finish. But a piece of answer and a stopwatch can give you more accurately , completely and timely feedback, and will be more helpful.
But that is quite special. generally, even for skilled people, to take an effective  study, an accurately and timely answer is needed.  And for unskilled people ,they need more  completely explanation to give them feedback.
Learn for practice, because we can get feedback through practice, when we learn to program, an compiler may give us good feedback, though it maybe not enough sometimes, so we need C Primer Plus and Google.
Some kind of feedback can only be given by people, a “positive” person who always say “that’s  good ” , and a “strict” person who always say “you may take more effort”, they can’s give good feedback to community.
If we want to learn “How to be a man ” in the society, we mean that the society always give us accurately, completely and timely feedback, but  it can’t sometimes.
No feedback, no one can take responsibility, so if you think a responsible people is good , you should give good feedback to the others. we all live in the society and we all have some responsibility to make it better.