I dont understand what oxycontin is prescribed for?

First of all I'm not some junkie searching for a way to score prescription drugs. I'm just simply curious. I have had 3 surgeries and also dislocated my shoulder and have never recieved anything but hydrocodone or oxycodone. I have heard a lot lately about the rise and dangers of oxycontin but dont understand how its so available to some people. When I dislocated my shoulder i blacked out of the pain and also was in severe pain for weeks. If that wasnt enough to prescribe that it seems like you would have to be dying to get it so why is it so easy for some people to get.