Removable pinch roller

[Thrashsmith]

Hello all, on my sheet metal pinch rollers the bottom pinch roller is removable, similar to this Edwards one I've pulled off Google.
Why? It doesn't help for getting a cylinder off the rolls. Or am I being thick?
Thanks

 

[Beanwood]

Perhaps so a shaped roller can replace it, for reducing wire diameter or something?

 

[bricol]

Removeable as a happy coincidence of being able to skew it for rolling tapered cones?

 

[tigdlo]

Llift the rear roller, not visible in the photo, and the workpiece will roll around the romovable roller in the empty space in the front of the frame.