I think it was because in the 80's the US was wealthier and systems with disk drives were a lot more common. People would swap games on disk, and there was les

I think it was because in the 80's the US was wealthier and systems with disk drives were a lot more common. People would swap games on disk, and there was less pressure to learn how the underlying system works. Having a disk drive also enables more complex, larger games, which would be harder to produce as a lone programmer. Contrast this with the UK - we had much less money, it was common to type games in from magazines, which is how a lot of us learned programming. We mostly had to make do with tapes, which limits the size of a game and its sound and graphics to physical RAM. It was entirely possible as a lone programmer to create a commercial level game with a few weeks of late night hacking.