Quoted from vid1900:It's not necessarily "artificial scarcity", but simply as the market saturates for each title, it does not make sense to keep producing a product that no longer sells.
Williams did not keep making Defender. When the market saturated, and sales tapered off, they then released Stargate.
When Pacman sales slowed, they came out with Ms. Pacman
Still not the same thing as advertising something as limited run and not producing more if the demand is there... they are trying to generate up front demand (likely to counter holding out for the well known discounting that happened with phase one).