I doubt they're made of special metal. The reason your traces have to be really wide is because they are very thin. Think about it, a normal copper wire may not be very wide, but its the same thickness in all directions, a trace on a PCB has width but very little depth, they're almost paper thin. Thats why you need super wide traces, but the wire (in this case connectors) dont have to be super wide.
Honestly, I could be wrong here, but this is what my intuition is telling me.