I don't think the collection of fake internet points is the main driver here.
A lot of questions with reasonably good answers are abandoned without being accepted, regardless if a bounty is set or not. The user has had their issue solved, if they don't want to interact further with the community then you can't force the issue.
Additionally your suggestion only works if the questioner is the one that set the bounty. What do you propose occurs if a 3rd party adds the bounty to the question?