From a worse than poor memory, those little power sockets were for accessories of the time, a time with very different expectations than today..?
One such accessory was a wander lamp, useful when working in dark places on the car, another was a parking lamp, again with a long flex, the parking lamp was sort of torpedo shaped with a red lens at one end and a white lens on the other and a clip designed to grip on the top a side window with the appropriate colour of lens facing the on coming traffic....perhaps more suited to a time when there were far fewer vehicles parked on the road, or if parked in rural surroundings with no street lights.
I also remember electric strip elements with a sucker at either end that could be affixed to the bottom of the windscreen or rear window of a saloon car to de frost it... In some countries I think the UV degradation may have been an issue for the insulators breaking up around the metal parts of the plug arrangement causing shorts...?
I might have thought that concours entry types might have gathered up such period accessories for an extra point or two... (-:
