@Hawkwinter You know what I learned recently?
Freeways were created in the US primarily so that the US military could quickly move equipment from one side of the country to the other.
Also, they wanted high speed networks created for communication purposes and at least one point in the 80s there was talk of laying fiber-optic cable down the median of the interstate to link everything together.
(Not sure if that ever happened, but it would make sense.)
You essentially have nationalized infrastructure, arteries that connect everything and while it has advantages for commerce, etc, my understanding is that the primary purpose was military logistics.
@oliphant @Hawkwinter They also placed them deliberately to destroy Black neighborhoods using eminent domain and called it "urban renewal"! Fun history.