Tagging an answer could help the algorithm as well as the users to identify to which topic it (also) might rever. Like hashtags in social media.
Example: tried to log in several times, sitting in the hotel lobby. Suddenly it works. Why?
Answer: Sth. without mentioning cyber security.
Using the tag cyber security would link the answer to this topic and might give orientation at first sight. Ususally the answer comes from s.o. with specialist knowledge who knows which tags are best to use