A pretty big reason as to why the roads around this area of the country are worse than others has to do with winter weather and the population. I would also imagine other areas that experience a fair amount to significant winter weather face similar issues. Money and state budgeting to fix said roads also plays in.
This is one of the most densely populated areas in the country and when winter weather comes along, the roads have to be in decent enough shape to accommodate for travel which leads to a lot more salt and other forms of road treatment being used. That stuff eats away at the roads which goes without saying and contributes to the roads being in lousier shape.
Some areas in those western states do not have that winter weather issue and even those that do at higher elevations, there isn't enough population to warrant as much use and more often than not for big storms, roads are just closed off entirely because they can do that without having to worry about impacting as many people getting from one place to another.
