There are some urban areas where the freeway is the only direct route to get through certain barriers such as railroad yards, culdesaacy suburban developments, over other freeways, and over railyard areas.
Freeways are also the most well known routes and people site them constantly when giving directions to places. They are usually the simplest way to get from one big city to another.
They are also the fastest route to get through any area and sometimes can be safer than congested arterial streets with no bike lanes.
If pedestrians and cyclists were all of a sudden allowed to use the America's freeway system in every state and city, what affect would that have on bike culture? Would pedestrians and cyclists not be able to handle it and get killed left and right when trying to use these facilities? Would they even choose to use these facilities? Would there be numerous pileups?
It seems interesting that America believes so much in freedom, and this was one of our founding principles back when the nation was first created, but now we've made it so hard to get places that it essentially requires us to use a car, drivers licenses, and license plates to do so.
Cars are basically treated as higher respected transportation over bicycles when they are given these special free-flowing facilities to get anywhere in the U.S. whereas bicycles are not given this.
I personally believe that allowing pedestrians and bikes to legally use all freeways would create a huge boost for cycling culture and it would really help kill car culture. I know more people would die as a result of it from accidents, but think of how much healthier our nation would be if biking was seen as fully supported by the state and cyclists were allowed to use every road? It would also encourage the states to build safer freeways and lower the speed limits on freeways if they knew that pedestrians and cyclists were allowed to use them.