It could also be that the drivers just plain don't know the rules of the road. It used to be, here in Washington, drivers-ed was a class available in high school taught by a state instructor. Budget cuts and privatisation took care of that. Now, if you want a license: Pay some fly by night operation to not only "teach you" in some class with little or no rules regarding that classes actual content, drive around the block a few times and that same instructor also gives the final exam! No conflict of interest there!

Also, given Washingtons explosive population growth, many competant people may simply not know Washingtons laws. (Match speed, then merge, or pull up to the white stop bar, anyone?...Lookin' at you, California.)

I get that some drivers are courteous, others not. I am thankful for those that are, even if they are ignorant.