I dont see why you would do this when there are apps such as ZBrush which let you express yourself creatively just as much, only without the mess and additional time consumption.
Because I like to use my hands. You don't have the physical interaction and 'connection' you do working in ZBrush that you do with clay (and other materials -- most if not all of them are equally valid for carving; I'm thinking about trying wood next).
if you were to make his skin any smoother and not jagged, how will you do it or when will you learn it?
Probably after baking with some fine sandpaper.