“I spent three days a week for 10 years educating myself in the public library, and it’s better than college. People should educate themselves—you can get a complete education for no money. At the end of 10 years, I had read every book in the library and I’d written a thousand stories.”
Being universal in your interests will greatly contribute to your writing. Each discipline you are interested in and study in will add to your knowledge of writing and style of writing. This is due to the fact that knowing many different disciplines will make your writing more multifaceted.
Being only a writer and not being interested in anything else can seriously limit your creative output. Even if you are engaged in sports or biology, it can aid your writing in a practical way.
Say you are writing science fiction: it is definitely a plus to know about the ins and outs of science. Most science fiction writers learn about science on their own, or even have degrees in science. Or say you are writing a poem: knowing history and social sciences will help you to write about people and events.
All knowledge is intertwined. A wider variety of knowledge means a greater capacity in all fields you work and play in. Writers are rarely single-sided people. They are curious in almost every field imaginable, as they have to present life in its entirety and reality.
So, if you are not interested in various fields as a writer, take up more activities in your life. Try a sport, study some science, learn more about mathematics, read some philosophy, delve into ancient history, take classes on social studies, visit museums often… these activities will help you to become a versatile writer.