If you have natural talent you don't need a coach (unless you want to be super-good). However, coaches (ours anyways) lays out a schedule for what you need to run (i.e. distance one day, speed the next, thresholds, hills, etc.). He also sets up the meets, gives announcements, gives personal advice, gives tips for running a race (it's far more complicated than you might think).

I like cross country because we get to go mess around in cool places and it keeps me in good shape.