Because you never know what you will find. This story in the New York Times got my attention. It concerns a most unusual penny and might make you want to examine more carefully the handful of change you receive back from everyday transactions.
I tend to look closely at coins, although I usually save them up for a while and then sort through them, then hand them off to dad, who is much more knowledgeable about matters numismatic than I. He has collected coins for as long as I can remember, and I grew up enjoying looking through his coin collections and learning about mint marks, milling, elements used in coin making, and so forth. It is still a hobby both he and I enjoy, and I can't imagine anyone I would have a better time with poring over such minute details.
So, enjoy reading the story about that special penny, and take a closer glance at the coins in your pocket today. Who knows? You may be sitting on a conversation piece.