Agreed, but you get that on a lot of forums.
In some cases, the original poster keeps coming back to read the responses, but doesn't have anything to add to the discussion (like if they ask if something can be done, and the responses seem to indicate it can't).
In other cases, they may lose interest, or simply give up on it.
I'm not sure how we can improve the situation. If people leave, they leave. We can't really force them to come back and post again.