I think we should legally require poker machines to never pay out, ever, and I think we should advertise that fact very boldly on the front. Seal up the return tray and put in a big sign that says "This machine never, ever pays out. You will not win. This is not a bluff or a challenge. We are not kidding." Then when you step up to one, you are under no delusion that you are about to win big, or that this week's welfare payment is sure to turn into big bucks, because there is obviously no winning.
You're already not going to win, long term, but this change turns this form of gambling from a tax on innumeracy to a dead certain black hole. Hopefully it would snap some people out of their addiction, but the effect will probably be more like a two-pronged response. The addicts will go elsewhere, like the lottery, and some will demand the return of the meagre payouts that kept their delusion afloat.
Mokalus of Borg
PS - For those who are playing "just for the fun", there's no change.
PPS - Except that it gets slightly more expensive.