The problem with allowing easy unlimited (or automated) re-searching is that the network becomes filled with too much noise. If there is too much information flowing through the networ, then the initial search (and any subsequent searches) won't be as useful. If you've ever seen the movie "A Beautiful Mind" (to use a popular example), it's exactly like the theory that John Nash proposed -- what's best for the individual is also (or closely tied to) what's best for the group.

It is vitally important that results arrive quickly to any user-initiated search. It is not as important to have them arrive later. Everyone asking for something all the time would hurt both goals, whereas keeping quiet helps both.