The depicted version looks a bit primitive. Why is there no spring loaded plate on the underside to keep the wire pressed to the metal above? (You know, an engineer who gets something in his hand will always try to find ways of improving it. [Linked Image] )

I'll echo Iwire's comment on getting the wire out. But, solder it? Are you kidding? Is that even legal?

The difference between a connector and a device might be there is vibration from the device? Or simply a different panel who makes the decisions, like Sparky says...