One thing I don't think anyone brought up in all these blackjack reviews, but which I think is a fairly important one: Blackjack is a "sophisticated game for adults", and having a "sophisticated game for adults" in your game library is a pretty big plus if you're trying to market these rather expensive devices to families. The market for these systems were families that included kids in grade/middle school and adults in their 40s, and back in the 70s, tank games and spaceship games weren't really something that 40-somethings were going to be particularly drawn to. Blackjack, however, is right up their alley (another obvious subject is chess, but that's considerably more complex to program and has somewhat less broad appeal, which is probably why everyone went for blackjack first), and advertising that "not only can the kids play cowboy, spaceman and soldier on this new entertainment system, the adults can also use it to play blackjack against an electronic dealer" is the kind of pitch that can net you a good couple sales.