An education (even a self-education earned at the library) gives you a systematic and detailed examination of a field of knowledge, taught by masters in that discipline, using the accumulated and accepted knowledge of the past, as well as the latest and most up-to-date thoughts of the future development of that field. It may be limited by the depth (or lack of) of your studies, or because you never applied it to your own life and combined it with the experience of practice, but it still gives you a glimpse into a vast world and a bit of understanding of it.

Even if you never use that knowledge professionally, or practice it to earn your living, it gives you an insight into that field of knowledge, a survey of its past accomplishments and failures, as well as how it fits into the library of all man's knowledge. It doesn't matter what the field is, or whether or not you ever are exposed to it again, it gives you an idea of how complex and rich all other fields of knowledge are, even if you should never have any experience of it at all. That understanding in itself is of great value.

I never took any courses in pharmacy, or Slavic languages, or microbiology, or the history of the Persian empire; but I know that there are people out there who know as much about those fields as I do about mine, and some who know a lot more. I have an understanding of just how rich and beautiful and detailed is the whole landscape of human knowledge, and how little any one of us sees of it. I have a good idea of just how much it is I DON'T know, and that is a humbling, but extremely valuable experience.