Spades has long been the standard card game in the US military, which is at least partly responsible for its widespread propagation. That is where I learned it, and most other people I know either learned it in the military or from someone that was in the military.
That said, I never played it that much outside the military. These days everyone seems to play poker.
That said, I never played it that much outside the military. These days everyone seems to play poker.