We meet new people, get to know them a little and often we choose not to spend the rest of our lives trying to know them better. A commercial for a new movie shows us parts of the movie and we often choose not to see the whole movie. We clean one room of a house and stop knowing another part of the house is in need of cleaning.
The ability to make the right choices of what we should and should not finish is what is important. I am a person who has a problem with starting to clean one area of a house, if I know I cannot finish the entire house. Worked well until I was a parent, was very difficult to get started once I realized I could never finish. I'm getting better at making the right choices, but it takes a lot of work.
It may seem unusual for someone to start a book and not finish it. Is it any different than all those less obvious things we start and not finish every day. All most of us can hope for is the majority of things we choose to finish are for the most part the better choices in the long run.