Why do points that are earned on closed questions count for the asker and answerer?
Just to close the loop, the reasoning is explained in this answer on MSO:
Closure is a lot more of a temporary state compared to deletion, especially when it comes to "not a real question". Generally, two things will happen - junk gets deleted (as apparently happened in your example question) or glorious revisions lead to reopening. One already results in reputation vanishing, and the other would require the reputation to be re-instated post-fact.