Not everyone is blessed with 20/20 vision. Some people can't even get their peepers corrected to 20/20 with glasses (I am one of those!). While sometimes blurry vision can be a good thing (bokeh photography anyone?) it's not always all it's cracked up to be.
I don't wear contacts because they do not improve my vision any better, I have dry eyes, and they require more maintenance than I am willing (or have) to give them. This makes a lot of things that some take for granted very difficult for me.