There are many possible motivations for reading, but here are the main reasons that I believe are why people pick up books:
1. To Discover New Places
In fourth grade I badly wanted live on Prince Edward Island with Anne, in fifth I despaired never going to Hogwarts and in seventh I was relieved to being free of the tyranny of Big Brother in Oceania. Books take your mind on a journey. They let you imagine new places, new experiences, people different than what you find at home.They also bring you on emotional journeys. You know you cried when Dumbledore died, and cried even harder when Dobby did the same. People read because books give you new experiences.
2. To Learn New Things
A fortnight ago I read several long sections of a 300 page long thesis on the effect that online reviews have on customer's decisions. Granted, this was for a research article I was writing on a related topic for class, but that didn't make it any less interesting. I read that thesis because contained in it was knowledge that I wanted but didn't have. This is the same reasons I read my textbooks, my scriptures, why I click on the silly articles on Facebook. All of these groupings of text have information that I do not, and I want that information. Learning, coming into new knowledge and vocabulary, is definitely a major motivation for why people read.
3. For a Different Perspective
In the third grade, my travel experience was essentially limited to visits along the West Coast. I had not been further east than Nevada, and certainly had no practical experience on any kind of unhilled land, but despite this I could picture life on the Prairie very clearly. The books of Laura Engalls Wilder were the primary source in my imaginations, and without them I would never have thought of what life in the Midwest was like, never mind life in the 1800s. Books give us a whole different perspective. Through a book I could be anyone else, be it a pioneer or a political leader or even an alien. Books let you see life from the point of view outside of your own and I believe that that is a major reason why people read.
4. To Keep Up
No one likes being left out. We read newspapers to keep informed, diet books to stay on trend, fiction to stay relevant in conversations. In middle school, every girl in the grade didn't read Twilight because it was good literature (it's not. It's actually really awful) but because all of their friends had read it and they needed to be ale to participate in the conversation. Gossip rags would go out of business if the need to be in the know wasn't present, and no one would read a biography for the same reason. One of the motivations behind reading is people hate being left behind.
5. For Entertainment
Books are interesting. They can be funny, or sad, or filled with action. People want diversion from their everyday lives, and books and movies provide that. I will never be in Elizabeth Bennet's situation, but goodness I found the way she handled it humorous. That is the main reason we read. It keeps us interested and entertained and make us think and gives us new ideas and things to day dream about.
