I tend to use in lines if I'm chucking very long distances as I find they are less prone to tangling, also for when I want the hookbait very close to the feeder.
They are often associated with bolt rigs but don't have to be, for example on a method feeder or anything that uses the same principle a change of the semi-fixed quick change connector for a swivel and bead makes it a very effective running rig.
