They tend to all look alike, no matter what part of the country you are in, except perhaps for the palm trees and graffiti which give our freeways a certain local character. A highway, on the other hand, is an experience unto itself. On highways, the scenery is always shifting and changing. You can pull off to the side of the road, if you want. People on a highway are in no hurry, though they know where they're going.
Freeways are for efficient travel.
Highways are for pilgrimage. Follow Route 66 far enough, and it will take you to St. Louis and drop you off at the window of Ted Drewes Frozen Custard stand on Chippewa Ave., the best frozen custard in the known universe. If all you want is ice cream, there are quicker and easier ways. You could fly to St. Louis, for instance. Or, if you dare imagine it, buying local brand of frozen custard.