Probably because they realise the current bubble is temporary so milk it while it lasts. Short term thinking really, but when you look at the median ages of the people who are at the upper hierarchy at Stern you can't blame them really for not considering the repercussions of their actions (pricing all but the most hardcore "home use only" devotees out of the hobby) and impact it will have on the next twenty years for pinball in the public mindset.

As an aside, it is slightly misleading to say that they are "still making title X". The reality is production on particular titles stops and restarts to fill customer orders as the demand becomes apparent via info from distros. And since Stern have admitted previously that 50 units of a title is sufficient for them to warrant putting a machine back on the line it gives you a baseline of the actual numbers involved. It certainly isn't the case that they are putting a machine back into production and then running off thousands more of them, that is for sure.