When I bounty a question I'm often looking for something specific or a significant level of detail that deserves it. I'm only going to award the bounty to a question that satisfies the criteria of my hard earned points - I'd say many people are in the same boat.
With this in mind - why is there a time limit on how long it is before I can award a bounty? I wouldn't think people would be doing this unless they truly felt the answer met all the conditions of their having places a bounty originally. I understand it's this way for a reason - curiosity is killing me though and I'd love to know what that reason is!