Amtrak tries to wash the equipment at each end point, but this isn't always feasible. There are some end points that don't have a car wash, like St. Albans, VT, Lorton, VA, San Antonio, TX, and others (granted in Lorton they do wash the windows, since it's home of the Pride & Joy after all). At some areas where there is a car wash sometime the trainset can't hit the wash, either because of the need to turn the train quickly, or a broken car wash. If you get on any train towards the end of a trip, it will likely look like hell, but so will anything that travels a couple thousand miles without being washed. Also, don't forget if you look at the mileage of most of these cars and engines they have MILLIONS of miles on them. Show me an automobile with just one million miles on it and it'll probably be rusted to hell.