Year ago, I read a romance that just bugged me. The author kept mentioning that the child couldn't swim. He was in a boating contest, and the child had real danger of falling into the lake. Did he? No. The author missed a huge opportunity to up the conflict for that story.
Why mention the kid can't swim unless you intend to use it later? Why have a doctor in the story unless someone's injured? Why have a cop in a story unless they have to hunt down a criminal?
In other words, why bring in anything if it's not essential to the plot?
That's a tough lesson for authors to learn, but essential. Every word is important, every plot point should propel the story. If it's not used in the plot, dump the situation.
If you're an author, look for these extras that aren't necessary. They need to go, because they just confuse the reader.
Have a great day!