Imperial measurements are more intuitive. I can visualize common measurements in inches, feet, and miles *FAR* more easily than centimeters, meters, and kilometers. Don't get me wrong, I can usually process metric measurements reasonably well, but it still takes me a few seconds to go from "42cm" to "about this long"; if I hear "about 16 inches", I don't even have to think about it, my brain just visualizes it with no noticeable effort.
Granted, that's probably because grew up using a lot of Imperial and almost no Metric, but it's still a valid point. Until the US gets a generation of people, a significant portion of which grow up using just as much Metric as Imperial, we're going to stick to what's easiest for us to use.