I think it's just the law of supply and demand. There so many people wanting into the electrical contracting business and there are always plenty of new ( green ) ECs so it's easier for the GCs to shop around.
In areas like this where only the owner is required to be licensed one master can put 50-100 people to work under one license and only a few of them need to have any real skill level. It can be easier to find those wanting to do electrical than finding carpenters or masons or even dry wall crews.
Makes sense