Thread forming tools literally just force mangled threads back into shape. Taps & dies cut threads, and chasers are a cutting or final finishing tool for threads. Personally, I think that once a thread is deformed, reforming it is fairly pointless as you've already lost the strength; better to recut. Only time I've heard a use suggested where reforming is a feasible option is on captive nuts which can't be replaced and have only a few thread depth, where you want to retain as much metal as possible. Won't be as strong as original, but I can see the point of using them there.
That's only my personal opinion though. I know how you lot tend to love reforming over there, over using the proper method and running the tap or die over something, so I ain't getting into that argument.
