In programming, you do a lot a writing. Probably as much writing as some best selling book authors but your books will never be read per se. Let’s use books as an analogy.
If you write a program from scratch, you are the author much like Stephen King. You plot and plan the story. You define the characters and their backstories. You write biographies of these characters that will never make it into the book but these details are important. In programming you do much of this same detail of work in project planning, database architecting, creating or choosing a programming framework, meetings and discussions with clients (book publishers) as well as your team, deciding what external resources will be used and so forth. You are Stephen King.
If you don’t write a program from scratch but instead work to modify a program that someone else wrote, you have to get into the head of that person. Much like if you were going to modify or edit one of Stephen King’s works, you’d have to get into his head, figure out the back stories, and really analyze the writing. With code, you have to figure out what the other programmer was thinking all without the documentation and backstories that were created during their process. You have to become Stephen King.
The people who use your program or the modified version of someone else’s program do not have to get as intimate with the works. They use it. Or in Stephen King’s case, they read it.