If you have ever been faced with the great challenge of helping an older person to learn how to read, you are no doubt well aware that it can be an extremely daunting task. While the desire may be there in force, it is simply not as easy for an older person to take on such a new skill as it is for a younger person to do the same thing. Skills are just that way- the older you are, the more tricky it can be to really make them stick in your mind. This is why our society is so adamant that children learn how to read as a matter of their most basic and earliest education.
Learning to read is what allows just about everything in this world to happen. If you can not read, then obviously going through a contract is going to be next to impossible for you to do. And if you can not read, then figuring out what is going on in the world is going to have to be done entirely through word of mouth or personal observation. Since you can not personally observe or gossip about everything, you are going to be at a serious loss for many topics.
Those few unfortunate people who can not read are always going to be marginalized in a highly literate society such as our own. They will be forced to accept things which the rest of us take for granted as not happening, and they are also going to have to be extremely dependent on people who can read, both within their own lives and in the larger context of the happenings all over the world. Reading really is fundamental.