why is there a dual element bulb in

I don't want to throw in a wrench here but how is a single filiment bulb going to work in a double filiment socket? That's not gonna happen. The contacts and locating pins on the side of the bulb won't even line up. Single filiment bulbs have even spaced pins - dual filiment bulbs have staggered pins. I have the same problem with my dome light. I am tearing the door switches apart hoping to find the problem. Why did they even make a dual filiment socket for the dome light anyway? Does that have anything to do with the optional "Map Light" switch located under the dash?