We are perplexed by the Time-Turner controversy.

We can only presume that JK Rowling created the Time-Turner because a story sometimes requires a little additional punch. After all, it allowed Hermione to become even more of a know-it-all by attending all of her classes, as well as saving Harry’s uncle’s life.
While this was an excellent application of the Time-Turner, why didn’t everyone have one so that nothing negative could happen? The premise is perplexing, which is presumably why she chose to eliminate them all later.