It seems to me like there's a pattern with it in regards to differences between Japanese systems and those from everywhere else. Most Japanese arcade games in the early 1980s borrowed heavily from Galaxian's model of tilemap+sprites which pretty much became the standard. But a lot of American games (e.g. Williams' Defender, Robotron, etc. and Taito America's Qix, Zookeeper..) used a big framebuffer & blitter. Maybe memory was more expensive in Japan.