At the occasion of this question, but there are many, many more examples where I notice a question which is bountied, but still a straightforward dupe. We then have to wait seven days to actually mark it as a dupe, for reasons of, I guess, not letting OP waste his or her bounty.
Existing dupe questions are sometimes difficult to find, and it is not by definition because of a lack of research that OP did not find the previous question/answer. On multiple occasions, I requested a moderator to refund OP for his or her bounty in obvious cases. Without exception, this was indeed allowed. This makes me think:
Why should we keep the rule that a bountied question cannot be marked as a dupe?