They are/were much used by us Joiners on site.
The wood cutting blades are useful if you need to cut a small hole in wall board, (ply/hardboard/upvc), to fit around an electrical back box or similar when boarding out a room, think 1970’s-80’s fake Oak planking etc!! They can also be used to start a cut for a larger hole so you can then use a tenon saw or panel saw. Not many jigsaws around back then, and no cordless tools.
The metal cutting version is useful to cut through nails and screws, when removing a timber door frame or window frame, which has been nailed into the brickwork, amongst other uses. Or even cutting through the bolt of a lock with no key!!
The Eclipse handle for holding a broken, or new, hacksaw blade are better. Sadly I don’t think they are available anymore.
Mark.