People who don't like to read don't read any books. People who like to read, but have no time might read only 4 books a year. They are probably reading other things regularly (journals, reports, textbooks) for their job or school and get their reading jones filled by that.
My husband reads 4 books a year, all on our winter holiday. The rest of the year he reads journals or textbooks or whatever for his work. He's about three years behind on those. He also listens to audiobooks while he drives to work, runs, works out, does other hobbies. He's been reading more books since I got him a Kindle, because it's easy to snag a few minutes here and there to read with it. He reads journal articles on it more than books though.