As far as standard primary wire goes how come no one uses it as much as the higher end brands.. I work at a hardware store and can get black primary wire of many different Gauges fairly cheap. Was just wondering

High strand count for flexibility is the main reason. That and a soft flexy silicone insullation.

You can use any wire you want even single strand house wire but it won't bend easily to install.

+1 You want insulation that doesn't melt easily and wire that is very flexible and can take a lot of current.