There can be enough difference in wages between states that many times traveling contractors have an unfair advantage. Thus the need for the prevailing wage laws. Too bad those rules cannot be applied in the private sector.
I'm so glad that Washington, (and Oregon), makes it plenty hard for traveling contractors to come in and take work away from the locals. It helps to even the playing field. I recently did a nice remodel of a apartment complex club house due to this. A traveling GC from Florida thought he was going to have his guys do the electrical just like in some other states. None of them had an electrical license of any kind, but even if they did it wouldn't have mattered here. You must be a Washington licensed electrical contractor using Washington licensed electricians. And to get those licenses requires a lot more than paying a fee.
RW