Originally Posted by U-I pilot

You arent missing anything. Thats exactly it...Priority. If you want to get on the flight, sometimes it IS necessary to be non-rev not jumpseat. You can also book a non-rev and jumpseat and if you don't use the non-rev then it doesnt get charged.

If you are a commuter this could be all the difference of showing to work or getting left behind. There are sometimes lots of jumpseaters more senior to you and thats a way to get on before them.....