I just had one of my answers deleted because it was the same as an answer to another question. However, I do not believe the answer should have been deleted. Sure, it's the same answer, but it correctly answers both, very similar, questions.
Why can we not reuse the same answer, especially if it correctly answers the question?
The questions have the same answer because they're the same (or almost the same) question: vote/flag to close one as a duplicate of the other.
The questions are actually slightly different and can't be closed yet both can be solved in the same way: modify your answer to address the specific difference in the question. Adapt it to fit each question asked instead of just copy/pasting.
The questions are not duplicates and yet there is no change you can make to your answer that would make it fit one or the other better: post the same answer, OK. Note, however, that in the 4 or 5 years I've been using Stack Exchange, I think I might have found one such case. It really isn't very common and that's why identical answers are automatically flagged by the system.