They are limited in their experiences, knowledge, and choices. Reading is a part of almost every experience in our society. You must be able to read to fully participate in the world around you. If parents sit and wait for schools to make readers out of their children, they will often be sorely disappointed. A love of written language and all that it can convey and teach begins as soon as children can see two feet in front of them.
Parents are the first step, naturally.
Reading with children should be as much a part of parenthood as making sure they learn basic hygiene, nutrition, and safety. It is that important. Children under two often have extremely short attention spans. Picture books, preferably with repetitive language and simple illustrations, would be the best route to take with toddlers. Children from two to four years old are usually able to follow simple story lines with more detailed pictures.