Nope, no reason at all. All you need is contact somewhere. It can be difficult to solder those. I would prep it and solder it before installing whether it was on top or bottom. You can also attach it other ways. drill and tap a hole or put a ring terminal on the wire and put the trem claw adjustment screw through it. It's kind of silly, you would think after all these years the claw would have a spot dedicated for the purpose.