I think it is huge. We live in a world where almost all information is written. Certain things are spoken and in video, but that is not very efficient and takes a lot longer to absorb. Good readers can learn things fast and absorb it better. If you learn things faster you can do more in school, work, and just about everything else that requires knowledge. People who are poor readers often get stuck doing manual labor jobs they don't like, since they can't learn how to do more advanced things which require good reading skills. This can have a huge impact on your life quality.
Good reading skills lead to good writing skills too, since you will learn how to write good by reading a lot. Good writing skills are also critical in school and work. Unless you plan on doing manual work, like work flipping burgers at a fast food restaurant, or digging ditches you need to become a good reader. The sooner the better.
